Looks like I'm in the minority on this one. I like BestBuy, and (as of yet) have had no bad experiences with them.
I buy from BestBuy both locally and online. My last major purchase locally was a Sony VAIO RS530G desktop computer in June of this year ($1349 with $100 mail-in rebate). Exact same price and rebate at the local Circuit City (and very close to online prices everywhere, but only CC and BB had this model available locally). I had done all of my pre-purchase research and purchase decision-making online, so I went shopping knowing exactly what I was after, and even knowing the stock availablity at each of the local stores, as of that morning.
Stopped at CC first, since I'd bought a computer monitor there a few years ago (before we had a BB in town) and everything had gone well. The salesperson who came to assist me was TOTALLY clueless. Looked (and acted) like a high-schooler, and knew NOTHING about the computer... When I told him what I was looking for, he said they didn't have any in stock. I told him that I had checked the stock availability online right before I had left home, and it showed they this store should indeed have the model on hand, so I asked him if he could at least double-check. Sure enough, he checked, and guess who was right? Even then, he led me to a totally different model on the floor, telling me the whole time that it was the RS530G, and I had to point out to him that it wasn't. I then proceeded to find the right model myself. Needless to say, by this time I'm thinking...OK...I don't think I wanna go this route...
Popped across the street to BB at the mall. Walked in, was offered immediate, knowledgeable assistance by a 30-something female salesperson. She knew what she was talking about, and she knew that I knew what I was talking about, and she respected that fact and acted accordingly. My purchase decision was finalized on the spot.
She offered the extended warranty, and I declined. She (politely) proceeded to spell out the benefits, and I (politely) declined again. She did not press. (More on this later.)
Then she told me about the store's policy of opening up all big-ticket computers and checking them out, to prevent the hassle of customers taking home any DOAs. I was delighted, and I asked her if they could go ahead and do the memory upgrade (from 512 to 1G) which I had planned to do on my own, but this would be MUCH more convenient for me. I bought the memory ($159), and gladly paid the $25 labor charge since it was worth much more than that to me to save myself the hassle of installing the upgrade on my own. I was anxious to get the new system home and get it up and running, so this was a great bonus for me. And, I was the one who asked about it...she had NOT pushed any upgrades, software, etc, and had only pushed the warranty as far as I noted above.
Prior to this purchase, I was not a RewardZone member, so I gladly popped for the $10 "membership fee", which would earn me a $65 reward on this purchase alone. I also had $150 in BB gift cards, which I put toward the purchase.
Great experience, and a great computer. It was repacked after BB's testing and memory upgrade, exactly as if it had just come directly from the factory and had never been opened, so my OOB ("out of box") experience was totally fresh and untarnished.
A month or so after the purchase, I received snail mail from BB, again offering the extended warranty. By this time, I had already re-thought and REGRETTED my decision to decline the warranty, so this time I opted for it.
You see...I've had bad luck with computers in the past. I've had two destroyed by lightning strikes, in spite of major surge protection, battery backup systems, and also the surge protection service and outside-the-house equipment offered by our electric company.
In fact, the computer which this purchase was replacing had just been destroyed as a result of a direct lightning strike to a transformer on a pole near the front corner of our yard. (It was a great HP Media Center Edition PC, purchased in June of 2003.) In this strike we also lost three phones, two answering machines, and 4 VCRs, plus phone service on both phone lines and both cable TV and cable broadband service for 2 days.
All the other phones, all of the TVs, all of the DVD players, the other 3 VCRs (yes, we had 7), my laptop, my flat-panel LCD monitor, my wireless optical mouse, my wireless keyboard, all of my external hard drives, my cable modem, and all of my powered USB hubs were all OK. And, some of them were on the exact same power supplies (and surge protectors and battery backups!) as the things which got fried. Go figure. Anyway...thank goodness for good homeowner's insurance. And, we had had a similar incident back in 1996. So, you can see why I had re-thought my decision and decided that the extended warranty might be a good idea after all, considering our history. So, I was glad when I received the second-chance opportunity to purchase it...and I just hope that I never have to put that purchase to good use, and that it will be nothing more than money down the drain. (Perhaps a little "good luck" insurance?)

Now, I'm planning to purchase a low-end Sony HT system (Sony HT-DDW660, for which I've read NOTHING but great reviews) for the bedroom in the very near future (possibly this weekend). It's $197 at the local Wal-Mart, and $190 at both CC and BB. I have a RewardZone 10% sale coupon (good this weekend only), a RewardZone $10 coupon, and another $50 BB gift card. Even after taxes, it should be about $120 out-of-pocket if I get to use the sale coupon this weekend...a bit more if I miss the coupon window. In any event...guess where I'll be picking up the system?
But, no, I will NOT be purchasing an extended warranty. Anything less than $500, I'd just as soon take my chances. If anything got damaged or destroyed, there'd probably already be a better, less expensive alternative on the market by that time anyway.
I'm totally appalled at all the negative experiences which have been related here, and I sympathize. The day will probably come when I'll have my own BB horror story to add to the pile, but, for now at least, I'm a very satisfied customer.
I also purchase some DVDs from BB even when they don't have the best price, IF they include any of the infamous BB-only exclusives. Otherwise, I genereally purchase DVDs and CDs online, from either Amazon.com of DeepDiscountDVD.com, whichever has the better price. (Almost always DDD these days, it seems. Plus, I've never yet NOT had a pre-order at least by the Saturday before street date, even with the free shipping option. NOT so for Amazon.)
For other things (other electronics, etc.), I go with wherever has the best price and availability, taking shipping into consideration if I have to get it online instead of local. Sometimes Amazon wins...sometimes BB...sometime Staples or TigerDirect, or elsewhere.
I really do wish that other online retailers offered the same degree of control over one's account that Amazon offers, though. Cancelling orders, switching payment methods, even on pending orders...totally painless. And, their One-Click ordering is great.
I also wish that BB would merge the online and the brick-and-mortar entities, at least so that the RewardZone program would apply to online purchases.