I'd definitely recommend watching and agree with pretty much everything that has been said. A lot of my friends who read the books years ago love the show. I first watched the first season and then I started reading the books and I read them all so far.
There are definitely changes, but I do believe that most of the changes are due to the constrictions regarding the budget and the amount of actors, sets and time they have available. They do try their best to keep things from the books, but a change here and there is necessary for the pacing and the overall wrap-up of the story. Someone already mentioned that they didn't really put a lot of information about the events from the past (as I first watched the show and then read the books, it took me two rewatches of the entire season and help from friends who read the books to understand Robert's rebellion and all that jazz), but I understand that it is difficult to just insert dozens of minutes of dialogue where someone is simply explaining history to someone else. And I don't think flashbacks would really be good either, it would be difficult to make it work.
Some changes already made the more hardcore fans angry (like the House of the Undying or changing Robb's wife), but there's a pretty obvious reason for those changes and, as I said, it's mostly due to the budget. Including the book version of the House of the Undying would require a lot more CGI and actors, so we got a watered down version. It doesn't really bother me, I read the books and I know what it meant there. It would sure be amazing if we saw it, but I kinda doubted we will because it's just too much stuff (and mostly cryptic stuff that would be too confusing, on top of being expensive). As for Robb, it falls into pretty much the same category; introducing Jeyne from the Crag would require a whole new part of the story with lots of actors and sets, so they just cut it and turned the character into someone who doesn't require portrayal of an entire new region just for Robb to meet her. I like Talisa from the show, and unlike the book, it made sense for Robb to betray Frey for her; in the book, his betrayal was much stranger. We don't see how Robb and Jeyne met and what happened exactly, Jeyne has only a few lines and there is honestly no proof that Robb would fall for her so much and risk his loyalties; the whole setup is just somewhat flimsy in my opinion. The show's version was much more natural and believable.
All in all, the show is very well done in my opinion and I would recommend watching it, regardless of whether someone read the books or not.