I have this too - seems to happen most when the OS is under "stress" (just booted, lots of Microb windows open, etc.). OS2007 had a bad tendency to miss touchscreen events under similar conditions (as does 2008) so I would not be surprised if they changed the driver and "key-up" is not being delivered in a timely fashion, hence the repeats. That's how it seems to behave on my N800, anyway.

In a related note, is it possible to change screen sensitivity and repeat? I swear you could do this in OS2007 in the Control Panel. Seems this has disappeared in OS2008.