54 weeks ago (I remember because it was the weekend of the NFC and AFC championship games) I was looking to upgrade size from my 37" LCD. I did quite a bit of research online and looked in person at most local stores and decided on a 52" Sony Bravia. Not necessarily recommending that over a Samsung, it's just what I liked plus I already had a Bravia home theater and they sync up nicely. I found the tv on amazon.com for about $300 less than Best Buy and American. I heard good things about amazon and their delivery service, but wanted to make sure I had it in time for my Super Bowl party, plus I'm just generally impatient. That Sunday it was in the American ad for the same price as Best Buy, but included a free Blu-Ray player ($300 value at the time) so I bought it at American. I guess the bottom line is it depends on how patient you are, but I definitely got a lot of good information from the customer reviews on amazon. In my experiences, Best Buy is fine for buying in person if you know what you're looking for, although I see one poster here had good things to say about a particular sales rep. That's generally not been my experience, but at least they aren't commissioned at BB. I think they are at American, and are generally higher pressure because of that. You may also find someone more knowledgeable there, because of that though.
Bottom line, I'd say just keep an eye on the Sunday ads, and amazon is probably good if you're patient.