I don't have much to add, but:

1) Use a trainer mat so that sweat does not go into the carpet. You can also pick up plastic stair/pathway covering at a hardware store for about 70 cents per foot. Get 6 feet and you should be good to go. However, I really do like the cyclops sweat mat and it does dampen noise also.

2) Riser blocks can be anything. I guess swiveling might be nice for a BIT more of a real feel, but as the bike si still fixed, I cant imagine it would be that great. I know people who have hammered a few pieces of scrap wood together, used phone books, or have a "real" block. Doesn't matter.

3) As for DVDs, I used the spinervals, thought they were ok, but not outstanding. Havent had experience with others BUT, the only thing that has allowed me to do hours upon hours inside on the trainer has been the Tacx Real Life Videos which require their Trainer and a computer. However, they also have something called "Video Cycling" that is very close to the RLV in that it is also a film of a ride (usually stages from grand tours or other races), that you would watch, but instead of the video changing speed with your effort and the trainer giving resistance to the effort, there are on screen cues that tell you what your trainer resistance should be at for the given portion of the ride. Might help the ride feel more "real" to you? They are not "workout" videos with someone telling you waht to do. They are just rides through the countryside, or up the Alpe D'huez and whatnot.

4) Yes, one can sprint unless it is a cheap trainer/poorly designed and does not have any stability (you will have less stability on a carpet depending on how thick it is. This is also predicated on the fact that when sprinting you don't throw the bike around like a puppy with a rope toy. Most sprinters put the power into the pedals.