My thought on 1.5.1 are simple. Mojang is taking Microsofts path- making everything way more complicated than it needs to be.
First off, as a texture pack maker, let me say this- Texture packs in 1.5.1 are the biggest pain in the a**. Every texture is it's own file, not to mention that every item is it's own as well.
Also, all of this new Red-stone crap, is unnecessary. Some may see it as "newer" or "easier" but we had all of this stuff before Mojang even got involved with it, so why fix something that even isn't f***ing broken? Back to the first sentence, Microsoft has the same problem.
I'm interested in hearing other thoughts on this. Let me know in the comments what you think of the new update. For me, Minecraft is just becoming a huge pain. Not good.