The new launcher is just plain annoying. Aside from it being an immense visual downgrade from the previous one, it is just un-necessarily complicated. Furthermore, switching between versions is a pain, as it deletes my mods (I only have two, but it's still annoying to have them deleted over, and over, and over...).
The lagg, too, is annoying. Ever since 1.5 Minecraft has been getting more and more laggy. In 1.4 I could run 256x texture packs with no problem! In 1.5 I had to downgrade to 128x. Now my minecraft is laggy no matter which texture pack, or version, I play on (I attribute this more to the new launcher, again).
The horses are awesome, though. I plan on, once the PMc server upgrades, dedicating my life to being a horse archer, riding along the country side raiding and pillaging.