Text editing in Powerpoint was dog slow and I was cursing every word I was writing in there. It was a big problem.
Then I found this helpful page which essentially says that any problems related to slow text editing are probably due to a bad printer driver or an old installation of the printer driver.
Solution: Make sure your printer driver is installed correctly
I checked my printer driver and indeed, it was not installed correctly. I quickly installed the latest version and voila - Powerpoint 2007 now works like a champ.
It seems weird and very annoying to me that PowerPoint performs slowly even if you don't fo any printing on it, just editing. Very weird, and very annoying.