I've purchased/worked with 6 different all-in-ones at work, family and friends. 2 epson's, a lexmark, a brother and a Canon. Lexmark sucked. It stopped printing very quickly, the scans were horrible, and ink was outrageous. Brother's ADF jammed with photo paper. Epson and Canon both had great customer service. Canon ink is cheaper, but size is smaller.
I prefer the psychological reassurance of paying only $12 for an inkcartridge with Canon (I own a IP3000).
If you do a lot of documents, get one with an Auto-document feeder. If you take lots of pictures, you can get one with a memory card reader that will allow you to print directly or copy to your computer. I would go with the one CNET recommends, it's been the Canon MP's for awhile now. Depends on how much you want to spend.