I didn't find it more stable AT ALL. Now that single player runs on an internal server, the game can't keep up with itself. Very often the game freezes (the game, not the executable) as if waiting for the server to say what will happen next. Just as often I find myself breaking a number of blocks, realising none of them dropped its corresponding item, and after a few seconds freeze, most of those blocks reappear and I am teleported back to a previous position facing a different direction. At the worst times, I had to perform actions (breaking or placing blocks) 3 or 4 times.
There is also plenty of sound stuttering, or the sounds of the last 10-15 blocks placed/broken and the last 20 steps all playing at the same time several seconds later than they should have. This becomes especially bad when there is a creeper around because with these freezes, the only warning I get is the fuse sound at the same time as the explosion sound, hopefully with a one second freeze to realise I am about to be blown up. Followed, of course, by the actual explosion.
So yeah, the update wasn't a good experience for everyone.
As for the new features, I haven't seen them all yet but they seem pretty interesting.
What I will give them is that the Nether is now as playable as everything else. Used to be pretty unplayable before. Haven't tested the End, but it used to be even more unplayable than the Nether despite being smaller.