I hate XCode but really want to love it. Most Cocoa developers have had more than a few bad experiences with XCode where it has crashed more than once in a day, magically, lost track of files, failed to warn you of naming conflicts in assets, or simply dead-locked your Mac; if you really want to watch XCode cry do a git checkout with a project open, that tends to bring things to a grinding halt, especially if there is a difference between the project files on each branch. This kind of thing becomes very frustrating as I am sure you are aware.
JetBrains has come to your rescue with their new AppCode. AppCode is an alternative IDE for Mac OS X and iOS development. It does a lot of things a lot better than XCode, but there are also some issues with it that prevent it from being a full replacement for XCode.
On the good side, AppCode offers much more advanced refactoring options than XCode, appears to be much more stable, has more intelligent code completion / suggestion. Like XCode, it allows you launch your App on your Mac, iOS device, or iOS simulator. It integrated with SVN, HG, and Git. I can’t speak to that features as I prefer to use source control from the terminal; it is also significant that as of XCode 4, Apple has added some Git integration into their offering. Unlike XCode, AppCode has full support for plugins and can even use the full range of plugins from JetBrains’ other products, such as IntelliJ. My favorite feature, other than stability, is Vim emulation; yes, AppCode allows you to use Vim keyboard shortcuts while editing if you prefer to work that way.
Naturally, AppCode is not perfect. In fact the issues with are less bugs and more that the product feels incomplete in a number of significant was. It cannot work with nib (or xib if you prefer) files directly. That’s right if you click a nib in AppCode you’re popped back into XCode. This goes the same for storyboards and CoreData data models.
These limitations prevent AppCode for being a full replacement for XCode. However, AppCode is significantly better for actually writing code and if JetBrains was able to get some sort of integrated Interface Builder functionality and CoreData model editing functionality, then AppCode would be a true alternative to XCode and would be my full time IDE.