I still have one of these (£60 import + cheap memory from auction site), bought it a few years ago.
It is very fast, I used to have XP Pro on it. Loading was very quick and windows was generally a lot snappier. I have Vista Business 32-bit now (won't fit) so I use it for my pagefile and general temporary files area (extracting RARs etc...), makes Vista a bit more pleasant.
The battery actually isn't required for day to day use (my one died and I have never replaced it). It is only required if you unplug the PC from the mains or turn the PSU switch off. It retains its memory even when shut down as there is always a little power going through the motherboard. The battery was block shaped, like those you get in some digital cameras.
Only problem with it is that it doesn't support AHCI (Intel chipset) so you need to set it to IDE or RAID mode.
Could you run some benchmarks on it HDtach or similar
Cheers