I have read some of the reviews (in particular, the ones that are not too positive) and I have to say: It still makes me laugh out loud... :-) OK, this season has several week episodes: The back-and-forth episodes at the beginning of the second disk are pretty boring. Seems that they did not really have something for a complete episode, so these are just patchworks of small bits and pieces. But the first episodes and the last about eight are really fun to watch
One big point of discussion seems to be: Not enough science. Too much personal life. I do not care too much that the focus of the series has changed. People change. Repetition is boring. My other two beloved series (House, Monk) really got boring when it got to the fifth season. Because nothing changed. Just more of the same. Only different.
I am a scientist (somewhere between Sheldon and Bernadette in discipline) and I *love* to see good jokes about the scientific part of their lives. But we had loads of great, great jokes on that front that at least I will never forget ("Geology is not a real science!", and the spherical sheep in vacuum joke, and the dark side of the moon). But people from science should be allowed to have a personal life, to change, to develop. (Sorry for my bad English.) And the focus on the more personal stuff is just cool because otherwise, it would get repetitious. Leslie was great, but only for some time. Kripke is definitely great, but I would not want his rhotacism (just got that from Wikipedia) in every episode -- it is only this funny. So, yeah: If you love the characters, and if you think that "a little different" can still be good, then the fifth season is good for you. Full stop.
I am more worried about the sixth season: They are so happy showing Howard floating through the space station, there is hardly anything happening in the first episode. But I hope that what we have seen in the finale will produce, again, something new and pretty crazy. I have always liked Stuart, and it appears we are seeing a hell more of him now! ;-) And finally, Rajesh has found somebody to love... How sweet! I hope for the best.