Well, I finally ironed out my PC issues that were preventing RMM installation, and I've had a day or so to put the Karma through its paces. While I'm certainly not at a point where I can make a good "go / no-go" decision, I do have some initial impressions. Some might be dupes of other peoples' experiences, but I think it helps to reinforce things. (+) are pros, (-) are cons. I'm going to leave out things that are said to be coming in the future like more visuals, etc.

Things I noticed in the first five minutes
1. (+) The size is not nearly as bad as some have said. Since I'd be interested in a 40GB model at some point, this is the size I'm more concerned with... If the 20GB is or were going to be smaller, that's great, but even this model is not large at all. Thicker than an iPod? Of course. But this wouldn't be a factor in my decision.
2. (-) The earbuds are no good. I don't like earbuds to begin with, but I've used earbuds that were not so bad. These are in my opinion poor in sound quality and very uncomfortable. The fact that they only include two of the little foamy things is bothersome as well, those are going to be the first things someone loses. The foamy things themselves should be made of a more comfortable material, since they're going to, you know, be in your ears a lot.
3. (-) Mine came with what could not possibly be described as a case. Maybe a "pouch." It looks like the kind of pouch I used to carry my Dungeons and Dragons dice around in. While functional for protecting the face from scratches, this is certainly not an ideal carrying case for a portable player. For a $400 portable device, it amazes me they couldn't spend a few bucks to include a half-decent case.
4. (-) The dock is well designed, but the neon lighting is cheesy. Obviously it'll appeal to some, but I wish there was a way to turn it off, especially when I'm sleeping.

Things I noticed during more extensive use
1. (------) The reboot problem. I'm on the latest firmware (1.11) and I'm still getting reboots very often. Every 3 or 4 songs in some cases. It's not related to any specific MP3's, since after rebooting I can go back to the same spot I was at and it doesn't reboot again until later. It's also not related to jolting/moving, since it reboots even when sitting quietly on my desk here at work. I have no idea what's causing it, but it sure does reduce the fun of playing with a new device when it reboots sporadically. Sometimes it'll happen twice within a half hour, sometimes just once over the course of an hour or two. I heard it was worse before, but I just want to point out that it's not fixed yet, at least not for me.
2. (+) Syncs over USB2 are awesome. Blinding speed. Love it.
3. (-) At one point today, the scrolling of long artist/titles sped up to a blinding (unreadable) speed for no apparent reason. A few tracks later it rebooted, and when it rebooted, the scrolling went back to normal. No idea where this one came from.
4. (-) I think the scroll wheel needs more thought put into it. I understand what the designers were trying to do, but I don't think it's ideal. A button press should be required to have it do seeks. Yeah, I know the control lock prevents against accidental button presses, but toggling that all the time gets old. The most common accidental control press for me has been the wheel rotating by accident. It's harder to accidentally *press* the wheel, so I think a wheel press should "activate" the wheel and maybe toggle through its functions (starting with volume, then seek, etc.) I think Mark suggested this elsewhere, and I agree that it's a great idea. I also think it should "time out" after a few seconds if it's not scrolled or pressed. If the scroll wheel does volume, then I'd allow the user to assign rewind/fast-foward to the volume buttons, since they're a lot harder to hit by accident.
5. (-) The "controls locked" message is unnecessary when you have a "lock" icon. Maybe pop it up the first time, or have a setting to disable it and rely on the user knowing to look at the lock icon or *gasp* the switch itself.
6. (-) Absolutely needs "tweak order" functionality. Your average consumer won't miss this because they don't know how handy it is... But coming from an empeg, this is the most glaring omission in the playback features. All the Rio DJ smarts in the world reduce my dismay at not being able to hear another random track from the same artist, year, etc.
7. (-) There's a brief but loud spike in volume when switching EQ's sometimes. This can be very startling if you don't expect it.
8. (-) The web server needs Hijack-like remote-control functionality for browsing and playing files from a web interface. Yeah it's a portable, but a lot of people will be using it at a computer, and would like to plug it into the network and control it that way.
9. (-) Scroll acceleration needs to be configurable. The way it is now is too fast for many (reading other forums) but I'm sure some will like it the way it is. The default should be slower than what's there now.

10. (---) My display just locked up as I was posting this. The music is playing, but the display isn't updating. I can skip to the next/prev track, play/pause/stop, etc. but the track playing screen (with the graph on it) is frozen. I scrolled the wheel while in this situation, and now the hourglass is on screen, frozen as well. And now I can't turn it off. Holding down the power button makes the hourglass turn over, but doesn't power down the unit. I guess I'll have to reset it, as soon as I find something small enough to fit into the reset hole.

Anyway, there are more (-) than (+) here because I'm looking at this with a critical eye, and this device was very hyped on this board, so I expected a lot. There are a lot of impressive things about it that I'm not reporting above because they were hyped prior to release (Rio DJ, good speed in switching tracks, organization features, etc.) I just wanted to document my first few impressions and see if anyone else is having some of the same problems (beyond what's already been posted.) As of right now I'm far less than impressed with the stability, even considering it's a brand new product. I hear there's a beta out there that addresses some of these issues, but I'm not privy to those releases, so...