I have a Kinetic and have logged more time on it than I care to count. Best trainer I've ever used.
They used to sell a little computer unit with it that sensed your wheel speed and did an automatic calculation to give you a power estimation. Don't waste your money, it's cheap and inaccurate (though I did once hit "1700 W" on it, which was an ego booster).
Other accessories you'll want (some already covered by others):
1. TV & DVD player or a computer with streaming video - A trainer does no good if you can't ride it for more than 10 minutes without succumbing to boredom.
2. DVD sets of whatever TV series floats your boat. I've developed a decent collection at this point. I've talked to various people about sharing these amongst teammates, but we've never gotten our s**t together to do it.
3. Buy a Bike Thong or similar sweat catcher. Sweat will rot out your headset, so cover it. $25 for this little terry cloth thing is a bargain compared to the cost of a new headset and the aggravation of having pull it out in little rusty pieces.
4. You can use a block of wood for a front wheel riser, but a storebought one will be nicer, and will help you avoid the scary feeling of having your front wheel slide off the side of the riser.