We agonized over spending $500 when we already were leasing the FIOS DVR, but after several months of use I can say it has been well worth the price. 

The picture and sound quality are excellent - perhaps the claims of THX improvements are real.  The user experience is much nicer than the Comcast or FIOS Motorola DVRs I've used, with the fast forward/rewind control, for the first time, a source of satisfaction instead of frustration.  The CableCard installation went smoothly, and TIVO's program guide and show descriptions are much better than either ComCast or FIOS.  And the 1000 GB hard drive is such a huge improvement over the 120-160 GB DVRs that I can finally say that I have enough room that I can watch everything I want in High Definition.

I do miss the 'On Demand' function that the cable/FIOS boxes provide.  On the other hand, they were frequently jerky and compressed, and the transport commands while in 'On Demand' were even balkier than the normal DVR functions.  I haven't really taken advantage of the Netflix/Amazon/Blockbuster streaming PPV option yet, so I can't compare how well they work.  I did connect to UTube a couple of times, but prefer to use my computer since searching and browsing videos is much easier that way.

Going with TIVO locks you in to services that use CableCards, so I was reluctant to do it until there was local competition.  Once Verizon launched FIOS in my area to compete with Comcast, I finally took the plunge.  In summary, I'm glad I got the TIVO and wish I'd done it sooner.