I thought I would post my experience of my T180 upgrade on here, as quite a few people will have bought one earlier in the spring when it was posted several times( got mine, base unit only from Comet for about £280).
Firstly, I took up the Acer Vista upgrade offer (about £14), the disk did take a few months to arrive, but there were no real problems installing it, except that the Norton supplied with the PC would work - so changed it to AVG free and all was well.
Except that the PC was much slower than with XP. So I bought the 2GB value RAM 5300 DDR2 kit from ebuyer. Struggled for a while to get 3GB RAM working, but eventually found that the new RAM needed slots 1 and 3, and the old 512MB RAM in 2 and 4 - since found out that this is the case for most 4 slot motherboards. Vista was now much faster.
I don't play a lot of games, but I do enjoy MS flight simulator. With the integrated 6150 graphics running at 1280x1024 on an old Ilyama CRT FS 2004 the background looked like a slide show if I increased the detail levels. Time for more spend I decided (also the old screen was not ideal for watching telly (Another posted deal I bought was Tesco direct's Hauppage USB freeview box £25, which works well with Vista). So I bought the Belinea 2225W 22" screen from ebuyer that was posted here £155 delivered, together with a nVidia 7900GS (according to the excellent Toms hardware site this gives the best frame rate for <£100 at 1650x1080). Also got the ebuyer 550W psu to power it (total £97 delivered). All the kit arrived promptly and went together with no problems. For picture / gaming the result is excellent - upgraded to Flight Simulator X for £9.99 (Amazon), and even this runs full detail at 1650x1080 at ~20 frames/sec - excellent. I am not particularly impressed with the monitor's display of text, it has some colour fringing on letters. I have tried adjusting everything I can find - the monitor geometry /phase control has most effect. If doing the upgrade again I would spend a bit more on the monitor, probably with DVI, and would probably buy it from a real world store that has a good returns policy. But at least I avoided Gordon's DVI tax on 20" plus monitors, that compensates me to some extent!
So in summary I now have pretty good system, particularly for games at a reasonable cost - I'm not sure how it compares to some of the recent Dell bargain deals posted - Dell seemed quite pricey though when I bought the Acer back in Feb. Thanks to all the people who posted these deals, and I hope this will help some people.