The first time I flashed to the 2007HE I stayed with it for about a day and then flashed straight back to OS2006.

The reason was that it simply kept crashing and re-booting the tablet constantly. I think it rebooted three times on me that day and as I *hate* rebooting the tablet due to previously having a wsod it was obvious that the 2007HE was a no-go. Btw I only installed Maemo Mapper on it after flashing the 2007HE OS so installing a load of applications wasn't the reason it was crashing.

I left it for a while and since I never had the tablet crash and reboot in 2006 OS I was happy enough.
I decided to have another go on 2007HE though for the hell of it.

This time it was a slightly better experience - instead of crashing and rebooting three times a day it now only crashed and rebooted once every three days which was quite an improvement.
However as I loaded on more apps - (not a lot - just rdesktop, maemo-mapper, the calendar and to-do list) the performance dis-improved.

When it decided to keep crashing and rebooting when when I tried to get an internet connection I decided to re-flash to 2006OS and despite the fact that the 2007HE OS is a lot prettier I'm going to stay with 2006OS from here on with the 770. It's never crashed and rebooted on me with the 2006OS.

Your mileage may vary but that was my experience.

I'm surprised (in a good way) that Nokia are bringing out the 2008HE OS at some point for the 770 but if it's as flaky as the 2007HE OS I wonder why they're bothering?