I can definitely see where you would find a dilemma in choosing between the two. I think the decision will ultimately come down to what you are wanting to use the device for the most. I've had the touch for a few weeks now and love, I also have some pretty small laptops that I travel with, though I don't have an ultra-portable, yet, so I will give you my experiences and hopefully this will help.
Since you travel a lot, you obviously know how important it can be to travel with as little as possible and to reduce as much weight as possible. The ipod Touch is going to take quite a bit of weight and size away, compared to the ultra-portable, even though it is small, it can't really compare to the iPod Touch. Don't get me wrong though, I was quite surprised when I opened the touch because the weight is very substantial. I was a little concered that it wouldn't have any weight behind it because of the size, but it really feels good in the hand. So overall, when it comes down to size, I think the iPod Touch wins hands down. It can do a lot of the things the Ultra-Portable will do, but in a smaller package.
Now, on the other hand, the smaller package on the iPod touch means a much smaller screen. The screen is very larger for a device of this size, but comparing to an ultra-portable, you will be losing some screen space. For watching movies, playing games and listening to music, the screen in perfect on the touch. However, if you will be doing a lot of internet surfing and things like that, you may find the ultra-portable screen to be much for convenient. I've been using the touch for a few weeks and have found the screen to work really nicely, but I don't use it for surfing the web that much. If you plan to do a lot of surfing, then the screen may become tiresome after a while. So, in terms of the screen, I think that the upper-hand may go to the ultra-portable.
In terms of capacity. I was originally planning to get 8gb, but then decided with applications and movies I may be better off with 16gb and so far I'm completely happy with it. I know that the 160gb of the ultra-portable is very tempting, but it also depends if you will need that much space. The main laptop I use right now has 160gb hard drive, I have tons of pictures, movies and music (including several copies because of having the songs on my different MP3 players) and of course my word documents, and other files, I've not come close to filling the hard drive. Obviously different users use different amounts of space, but it really comes down to whether you need that much space, or if it is mostly appealing because of the size vs. price. For the uses of the touch (unless you have a huge music collecton or video collection) I think that 32gb should be plenty for most users. Obviously you cannot store everything on there, but videos and things don't necessarily need to be on all the time, I personally remove videos once I watch them as I have not interest in watching them again, at least on the touch, I prefer to get something new to watch for the next time. So in terms of space, this is a toss-up depending on how much space you will ultimately need.
Battery life: Both devices are not going to provide a ton of battery life, however, I think because of the size the iPod Touch will most likely give you the better battery life of the two. For music the battery life is great, for vidoes, games and internet, it is decent. For the ultra-portable you would be able to charge anywhere, for the iPod Touch you would need to buy an accessory so you could charge in a regular outlet (you can get a generic one for around $15 and I believe the Apple one costs $30. ) I can generally get by with charging my touch once a day, less if I'm mostly listening to music. With my smallest laptop I try to do as much work as possible while it is being charged and then can get by with a couple of hours without being plugged in. So, in terms of the battery life, I think the touch would be the better option of the two.
Features: I think that both options provide a lot of options as far as what you can do, but both would depend on what you plan to do to determine which is the winner. If you plan to do a lot of computing, the ultra-portable will be the winner, hands-down. You have the larger screen, larger keyboard (a must if you will be doing a lot of typing. you will get used to the virtual keyboard, but even with practice and time, an actual keyboard will always be a little easier if you are going to be doing a lot of work) The ultra-portable also allows more functionality as a computer, giving you the ability to work with more documents (and in an easier fashion) as well as install programs that you may not be able to use on the iPod Touch. I'm not sure if you require anything special with your job, but if you have to have any programs, the touch may not be a good option. So, the ultra-portable gives you all the functionality of a computer, in a smaller format, while also allowing you to have an entertainment aspect as well.
On the other hand, the iPod Touch allows you to listen to music and listen to it with much better quality, as I'm sure the ultra-portable will not have as good of sound as a dedicated music device. You also have the ability to watch movies, play games, surf the web and use the various apps that Apple offers. The apps are great as they offer so many different options and really can become addicting and very helpful once you find the ones that work best for you.
So, in terms of features, the ultra-portable will be the winner if you plan to do more computer related tasks. On the other hand, the iPod Touch will take the victory if you plan to do more in regards to entertainment.
I think both options will work great. It all comes down to what you plan to use it for the most and what features they offer are most appealing. And again, a big thing to consider is size, they are both tiny, but with the touch you can throw it in your pocket and go, with an ultra-portable you would need to have a bag or something to get around with it.
As the other post said, it wll definitely be worth waiting to see what is announce at the event and see if anything works for you. I am personally planning to get a Macbook Air soon. I'm not sure if this is portable enough for you, but for me I think it will work great. As far as the weight goes, it is quite lite and not something that would be an issue for me. As far as size, I think it will great. If you can manage to take a messenger bag with you, the Air isn't much bigger than most magazines and legal pads, which when I travel are always in my carry on anyway. I still plan to keep the touch and take it with me as well, but as far as work is concerned, I still need to have the functionality of a latop, but want something that is going to be as small as possible and something like an ultra portable just doesn't work for the work I would be doing.
Hope this helps and doesn't cause more confusion... Good luck with your decision, I know it can be difficult sometimes!
