Mugglenet has a page which lists some of the major media reviews of HBP that they could find links to and most of them are pretty positive. And most of the individual comments that I have seen on fan sites and newsgroups till now are overwhelmingly positive with a lot of people saying this is one of the best (or outright best) of the series. Some people might have a problem with the romance angle of the book which might be considered to be somewhat overdone. However, for people like me and Jeet who loved Barb's fan-fiction of the closing trilogy - which had much much more romance than this - should like this a lot.
For the list of media reviews, go to this page on mugglenet. Specifically, the Time review is here and the N Y Times review here. Beware of spoilers though. Most of these reviews talk about the plot and I'd have hated to have read them before reading the book myself.