I just bought this scanner to replace an HP scanner that just decided to stop working one day for no reason whatsoever.
I cannot praise this scanner highly enough. Set up was simple and the TWAIN software is head and shoulders above HP's so called "PrecisionScan Pro". It produces much better scans than the HP and the nifty slide and negative scanning features are a huge bonus.
Downside: it is not the cheapest scanner out there, but if any of the cheaper Canon scanners are half as good as the 9900F, they are worth it. I am now a happy camper after several frustrating weeks with the HP and will be scanning a bunch of old pics, slides and negatives over the next few months.