For what it's worth, I have both an N900 and a Sony UX1XN (modified with a Core2Duo and I've swapped the standard 32GB SSD for a 64GB SSD). I have also owned an N800 and an N810 in the past. The differences between these devices are only really relevant if you have need to use them. For the most part there is little to choose between them in terms of surfing the web, accessing email, even satellite navigation etc. Yes, the UX eats batteries and yes it is HUGE in comparison to the N900... but can you play UT2004 on the n900? For me, the UX has replaced my previous laptop, and the N900 has replaced my previous phone. None of the UX's keyboard shortcomings matter when it's docked!

It really just depends what you want / need. No use arguing over which is best really.

Oh and comparing used ebay prices for a 2-5 year old UX against new retail prices of the N900 makes absolutely no sense. The UX cost a lot more when new!