Those comments may be somewhat out of date, since the website redesign appears to have been complete for some time. I haven't ordered anything recently, though.
I've never used them, but go to dvdpricesearch.com and at the very bottom of the page, click "More vendor info", then click on their name and "user comments" you'll find over 250 comments about their service etc.
They certainly were pretty difficult to deal with while almost nothing was working on their website.
Now most functions seem to be working, although you still can't cancel individual items from an order (must cancel whole order), their online returns process doesn't work and their email from the website doesn't seem to work, but they have been very responsive lately to any emails I have sent (not through their web site) and the issues I have had have been quickly resolved.
If you had asked a month or two ago, I would have said steer clear, but now they seem to be OK and certainly are the cheapest place around for many titles.
I've had no problems with preorders, in stock items and out of stock items. I had read some bad reports about long delays with out of stock items but they seem no slower at get stock in than anyone else I have used.
They do charge your credit card when you place your order, so I tend to time my orders to fit my credit card billing cycle.
I have used them several times in buying season sets of tv shows. They always had the best prices for example, Buffy, Futurama, Angel. Shipping always took a little longer, but that is because they are a canadian store.
I no longer purchase from them, but not because of anything they did. But i would recommend them if you want to save a few bucks and are not worried about getting titles on release dates.