Does it get better?
Um. Depends who you ask, I suppose. I found parts of S4 brilliant. Other parts, not so much. Episode 7 was John Quixote? Which I enjoyed a great deal, although it turned out not to stand up as well in the context of the rest of the season, in hindsight.
The next several episodes are pretty much one-offs, and 409 and 410 were not particularly popular. 411 is very important. 412 can be skipped ETA: except for the tag. End edit. Watch 413. 414 isn't important except for the bit at the end, sigh, and some entertaining character bits ("Oh, you don't scare me, missy. Okay, maybe a little.")
I hated 415 and you can skip it except for the teaser. It's a complete waste of an episode, and every character in it is moronically stupid. 416, on the other hand, is quite good, and it sets up the big finale for the season.
417 is ambitious as hell, and there's some fabulous acting in it, but it's not nearly as great as they thought it was. Still, I love the very last scene, and Ben Browder breaks my heart in it.
418-422 is the blow-out finale arc. 418-420 were pretty good, but 421 made me crazy because they dropped a lot of balls they'd put in the air. Some things made no sense at all, and I was very dissatisfied with some of the characterizations.
422 is... I have only seen it once. It's not bad, actually, although the ending is, well, somewhat controversial.