So my initial impressions:
1) The voice commands are working for me maybe 90% of the time. The rest is typically because I'm saying something the wrong way. MS needs to do some work here and have multiple ways to do the same thing and make it more conversational. Also, making me say the full name of things is stupid, I understand a problem exists (what happens when Forza 5 comes out.. you can't just say "Play Forza"), but there needs to be a better middle ground than as current.
2) I'm personally not seeing a big jump in visuals from 360. Everything so far looks like a really nice version of what I'm used to. Probably because both systems are less powerful than high end PCs and we've been seeing game media that looks this good for a while. That said, it's nice to get solid 30/60FPS in the games and overall better visuals.
3) Love the UI. Love Xbox On/Xbox Turn Off. Really like the TV interface a lot. Love the snap features for TV. Will make great use of that during sporting events.
Basically, I don't think either system was worth getting for the visual jump from PS360, maybe that will change, but the UI here is amazing and makes it feel like a real step up from the 360.
Very happy with the purchase overall... need to pick out a few more games to buy over the next few weeks. My wife is also in love with the system and she hates games. Once these things can be had for 250 bucks they are going to sell a ton as media boxes.
Also, All digitial future FTW. It is so nice not having to hunt for disks to play my games.