The new Tivo HD is a great box. I have an Series 3 upgraded to 750GB or 100 hours of HD. I've got tons of shows unwatched to hold me through the writers strike... I have a dual tuner Series 2 and with the new firmware, I can share shows (SD) between boxes.
I set my inlaws up with a Series 3 and Tivo HD. Now both boxes share HD shows between them.
I have all the boxes connected to our Macs and iTunes. Now all the Tivos can play music and photos very easily.
Yes, you pay for Tivo, but IMHO it blows Comcast's s/w out of the water. I can't speak for Tivo's Comcast s/w as I haven't seen it, it's only beta in New England. But if it's close to Tivo, that's also a great solution.
Now to your questions:
1) "How good are those new TiVos?"
ANSWER: Very good. MUCH faster than the HD DirecTivos. The HD Tivos are a great price point. I've heard they are slightly slower than the S3 but I didn't notice it. Heck, it can't be any slower than the HD DirecTivo, which was almost as slow as Sarah McLaughlin's Angel...
2) Any other features we'll lose?
ANSWER: Correct, no on demand. There's some brewing about switched digital video but I think that'll take time to roll out. For now, it's a don't care, at least for me.
3) Is the box responsive?
ANSWER: Yes. Much faster than previous boxes.
4) Anyone using TiVo as a networked music server (replacing the jukeboxes)?
ANSWER: I've started to. W/ iTunes, I'm pretty impressed. So much so that I'm about to regret the Sonos I made my inlaws get... I've tried the Rhapsody service that's new to Tivo, it's decent and the sound quality is actually quite good. I'd never subscribe, but it's nice to have the option. Now if I could have Pandora...
5) Anyone have experience with WeaKnees and their higher-capacity TiVo mods?
ANSWER: Yes. I upgrade myself and it's not too bad. I've bought pre-formatted and done it myself. I prefer now to do it myself and just find or buy the CD to format your drives. You can find it on
http://www.dvrupgrade.com/dvr/stores/1/. It's doable if you're comfortable opening up a PC and moving jumpers.
6) Anyone try downloading movies to the TiVo via Amazon's "Unboxed" service?
ANSWER: Yes, and it's not too bad. But it's not HD.
Something that I've found useful w/ my kids. I can now pull shows in SD and HD off all my Tivos. I move them to my NAS (network drive) and then convert them to use on an Apple TV and iPhone/iPod. GREAT for taking shows on the road. I don't have to buy DVDs and I can restrict my kids to PBS shows, rather than having them watch every Disney movie under the sun when we go on long trips.