Too Slow Rated 3 out of 5 stars
Performance on delta creation (i.e. when a changed page notification is clicked to open the change page) is pretty awful, and generally freezes Firefox for 5-15 seconds while it works. None of the other extensions I've tried do this.
User interface is simple, which can be nice, but for my needs is inadequate. Also, the appearance of the deltas is rather unpleasant, as styling seems to be removed.
On the whole, I don't recommend this for serious use because of the performance problems. If you can live with that, though, then it might work well for you.
I can't reply properly in this review section, so please post bug reports in the forums at http://updatescanner.mozdev.org
The things you mention have all been improved in the latest beta, available from the forum.