When Atlantis arrived, where there was a negative review, it was often pointing out that Atlantis was more or less SG-1 in a set of different clothes, and it is, no question about it. Substitute Altlantis for the SGC, Sheppard for O'Neill (and most of the team have a very similar counterpart in both series), and the Wraith for the Goa'uld, and there you have it- there is very little to tell them apart. Viewing figures dropped off, and Atlantis came to an untimely end (and believe me, I'd have been as pleased as anybody if it had kept going). So, now it was time for something different.
I can't comment on the similarities to Battlestar Galactica as I've never seen it, but the new direction is very different. Most of the conflict is internal, and there is far less full on action, but the plots (and the whole story arc) kept me interested. I can understand why folks with a limited attention span might find it hard to watch without a pretty explosion to keep them interested every few minutes, but for those who enjoy a bit more characterization there's plenty here to enjoy. Not that the show is devoid of action - there's still plenty of drama in the mix if that's your thing, but the ratio has changed from being driven by plot to a more character-based focus.
I've enjoyed the fact that some of the characters I liked at the beginning I didn't like so much at the end, and vice-versa. I've read one review that was of the opinion that the selection process for a mission like this would weed out any 'undesirable' personality traits that lead to the internal conflict with the people involved in this type of scenario, but I disagree. There would always be personality clashes in a situation like this- call it going stir crazy if you like, but one way or another it would happen. Many of the clashes lead to consequences in future episodes, and I like this - there is real cause and effect in what our characters get up to.
Another nice addition is that as the series progresses, we are fed little insights into the motivations of our characters, and this helps us understand why they do the things they do, even if it it doesn't necessarily justify them. Sure, there are several borderline stereotypes in the mix (and one or two well into the territory!), but that in itself is nothing new in the Stargate franchise. At least the characters are being fleshed out a little for once.
I've also seen reviews complaining of deus ex machina type resolutions, but to my mind these are far less in evidence than in the earlier Stargate incarnations. Not all endings are entirely happy - more evidence of those 'consequences' I mentioned a couple of paragraphs ago.
I can see how some folks haven't taken to this if they were expecting more of the same, but I've loved every minute of it (I've been watching these all week after getting home from work) and can't wait for the next season. The usual Stargate cliffhanger ended the series and I'm eager to see how it all works out. Unfortunately for me, I don't have any channel it's on, so won't see it until the DVD release around this time next year. I'm sure there's plenty of longevity in this series - whether it gets enough viewers to justify a third season (the second season is due to air in late September 2010 in the US, I believe) is another matter - I certainly have my fingers crossed for it.
So, in short - I love it. Whether you do or not is largely down to what you expect. If you just want more of the same old Stargate, then you may well be disappointed. I went in with an open mind, expecting something different from what I know, and I thoroughly enjoyed it. I'm no fanboy, prepared to defend it to the exclusion of all else, rather someone for whom the new direction has 'worked'. I think it may be very much a case of horses for courses and all that. Suck it and see, if you will - it may 'work' for you too...