I was so fed up with 1.5 (stitching, severely reduced performance) that I actually downgraded my version back to 1.4.7 for a while. But after 1.5.1 was released, I decided to give it a try. The results have been very satisfying. The performance isn't quite at the level of 1.4.7 for me (on my OSX iMac), but it's more than sufficient. And the stitching is gone. There are a few minor bugs (such as a glitch hopping into and out of minecarts), but on the whole, I'm finally able to enjoy the new update.
It's just odd that the new version needed a rapid update to properly function.