I picked up an EEE 901 recently
http://www.elara.ie/products/detailsfull.asp?productcode=MMEB994662&productID=S5712688 (not from Elara mind).
The machine is great, perfect for surfing on the couch etc.
Keyboard is a bit small for serious typing though, but grand for occasional use. The numbers are offset one key to the left which is annoying.
Screen is slightly small, but thats the trade-off for the small overall dimensions.
Its light & battery life is good (4-5 hours).
The trackpad is a bit juddery (apparently a Linux issue, should be OK in XP)
20GB SSD was a big draw, as it can take knocks and bumps a bit better.
BUT (and its a big but):
The Linux on it is dreadful - I had to reset it to factory settings within an hour of using it ... all because I tried to add/upgrade an application.
Very very disappointed in this, as I had intended to use it primarily under Linux, and put XP on it only if necessary.
The word on the net is to not use the add application in the standard menus.
Now I've 2 options - put XP on it, or change it to Ubuntu. Either way, I can foresee a couple of evenings installing / tweaking "fiddling" to get it going properly. Not what I had in mind really.
Software:
I got it working OK with the wireless network and NAS, won't work with the network printer (Brother MFC5460CN - windows only apparently). I'm not even going to waste my time trying to get phone/mp3 players, oddball work-related software etc. working with it on any version of Linux. XP for all that.
I'd only recommend a Linux version of these if a) you don't intend to be adding too many applications & are happy with the standard offerings (which to be fair are good), or b) you know your way around Linux and don't mind fiddling with it every time you add something.
RAM and OS Versions:
Ram is upgradeable, and it was available in XP (but with 12GB SSD, not 20GB).
If you're getting a Dell with Ubuntu, it should be cheaper and/or have more features as Ubuntu is cheaper (free?) than the cost of a Windows XP licence.
The EEE 901s have bluetooth and 802.11n BTW
I'd give the EEE 901 a 9 out of 10 if it had XP on it, with the rubbish Linux its a 6/10