Reading a Q1P review and Steve's comment it made me realize that I should make this point. In my opinion, a UMPC is a laptop / tablet replacement that gives you a smaller form factor and lighter weight which is a plus when you are not sitting at a desk or other horizontal work space. It gives you the power of a PC to take more places more easily than a larger, heavier laptop or PC. What it really is not, is a replacement for smart phones, blackberries, handheld gps devices, ipods etc. The UMPC is not pocketable, has a short battery life and takes some time to boot up.
In Steve's comment, he mentions that he used a handheld gps unit instead of a bluetooth gps receiver with his UMPC because his Q1P battery would have died before he finished his bike ride. I would assume that handheld gps receivers have battery lives at least over 10 hours while the Q1P with an extended battery lasts only 5 hours. What he did use the Q1P for was to upload the photos and gps information and create the tagged map, a task that required a PC. The advantage here was he was able to do this on the go instead of waiting to get home. He was also able to do this standing up, something that would have been difficult with a normal laptop with keyboard.
In the Q1P review (sorry, lost the link), the reviewer stresses the point that the Q1P does not have a keyboard. Personally, I love keyboards. I'm a very decent typer and can input lots of text very easily with a keyboard. However, I really don't miss an integrated keyboard at all with my Q1P. Mainly because of the way I use it. On the go, standing up etc, it would be hard to use a keyboard. Using ink or the TIP is much easier, like writing on paper. Of course I use a keyboard alot, when I'm at my desk like right now. When I'm away from work or home and I need a keyboard, my BT foldable keyboard does the trick.
As for listening to music while on the go, I will always pick the iPod Nano I own. Its very light, powers up quickly, is pocketable and has long battery life (greater than 10 hours). However, if I want to watch a tv show, video or movie, then the Q1 is ideal like when I watched episodes of Lost and The Office when I was on the train traveling back from Boston.
So I guess my point here is that UMPCs, in my opinion, are ideal to use in some situations. As my primary PC, I actually prefer it over a laptop. However, for those extremely mobile situations where the full power of a PC is not needed, I prefer to use other devices such as iPods, etc.