Day 1 of using my transported T42 laptop XP build for real use. Here's some feedback.
Observations
1) Annoyingly I'd say that multi-monitor support is incomplete and not usable currently. The reason for this is simple - Parallels creates a large single desktop over both monitors (taking the lowest Y resolution of both monitors).
This means that when XP opens a window at full screen it will do it across both monitors.
Second annoying thing is that modal dialog boxes appear in the centre of the desktop - as this is spanning both monitors then dialog boxes also appear spanning both monitors (half on each).
In short the stretched desktop removes the information from windows itself hence the resulting user experience is dire (I'm not a blind mac fanboy).
2) Even with windows running 16bit and the second monitor set to "thousands of colours" in OSX the memory usage of Parallels is high - infact it uses all the free memory, the inactive is not that large, the active portion gets large but the wired area is very large (I assume this is because this is the only way Parallels can get a continous sequential block of memory for the VM).
This makes running in cohesive mode/multi-monitor, to be quite frank, a gimmick unless you have over 4GB of physical ram (read MacPro only).
This is with a 1.5GB system ram with 16MB of VRAM configured in the VM.
For this reason I've resulted in dropping out of using two monitors as I used to use with my trusty IBM T42 in favour of using full screen with just the MacBook Pro's 1440x900 desktop. This does mean that there's not much to differentiate Parallels from other VM products so far.