I have the Canon 1220u. I love it... I also have a Canon Ixus V, and together they're great. no problems with drivers, never a problem with the scanner... so if the 650u is going to be half as good for half the price, go for it!
Canon make great gear (I don't like there printers, but I am yet to try the printers with the individual ink wells for each colour... so the jury is still out on that) so I recommend looking into there stuff.
What are you going to be scanning? This is important to what sort of scanner you need.... remember that what you need is far more important than what you want.
