Finally got a chance to install this build on my laptop last night. Took about 40-45 mins to install (P4 2.4, 512MB, 30GB 4200rpm drive). Overall performance is noticeably better than 5270, especially after defragging the drive, but I ran into more issues this time than I did with 5270.
Firstly, drivers for the ATi Mobility Radeon 7500 are not included anymore, not even on Windows Update. I managed to install the Omega drivers for XP, and things seem to be working well. Unfortunately, the reg hack to enable Glass on this card no longer works in this build (I knew it wouldn't last very long), so I'm stuck with the boring gray UI. Glass looks sweet, but I wish a little more effort would go into polishing up Express for setups with lower-end GPUs. Again, due to the unsupported GPU/drivers, I can't even open the new Windows Movie Maker, DVD Maker, and a couple of other apps.
This build of IE 7 has some serious issues with the XP Synaptics drivers that I installed for the touchpad. After installing the drivers, I can't open IE any longer (it crashes at startup), and looking at the Event Log reveals that there's some conflict with a Synaptics DLL. Ouch.
Office 12 Beta 1 TR seems to have problems connecting to my Exchange server (had the same problem with it on XP as well), so it looks like I'll have to reinstall Office 2003.
I'm a little disappointed, but I probably shouldn't be expecting miracles on a three year old laptop with a stone-age GPU. Still waiting to get a new HDD for the desktop so I can test this with the Athlon64 4000+ and 6800GT.