I've also been looking into ARM lately. As an everyday Linux user (Ubuntu), fortunately I wouldn't suffer much (if any) from switching to ARM, as Ubuntu runs on (some of) these devices as well.
I've also noticed the Trim-Slice, but what turned me away from it was its hardware accelerated video playback support - which is absolutely necessary for an ARM system to play back most video - only supports H.264 Main Profile (http://en.wikipedia.org/wiki/Tegra_2#Tegra_2_series
) which won't cut it for most HD content (and indeed most H.264 content). But if you don't watch video then this of course won't matter at all.
There is another company that does ARM computers with Linux, they're called Genesi
. Their products are based on the Freescale i.MX51 - and soon i.MX53 - platform, which is a single core ARM Cortex A8 clocked at 800 MHz and 1.2 GHz respectively. It's too bad Freescale hasn't released their Cortex A9-based platform yet, as I think the step up from 1.2 GHz A8 to 2x1 GHz A9 will be more than noticable (the A9 is out-of-order vs the A8 in-order architecture, among other things).
The cool thing about the Efika MX products - as they're called - is that the newer i.MX53-based Smarttop (Trim-Slice equivalent) and 10" Netbook will support H.264 High Profile 1080p decode. When software support is ready.
Which it's not as of this writing.