I used it for a couple of days, then switched back to TextMate. I am going to watch the PeepCode Vim series (http://peepcode.com/products/smash-into-vim-i) and I think that will give me some momentum.
Mhh, it takes some time to get accustomed to vim but it's worth it. Just don't give up too early.
I'm using XCode and vim ... XCode for iOS development and for everything else vim. Prior to that I used TextMate ...
After a few weeks of constant vim usage it happens that I start typing vim commands into XCode (or into any other bigger text field). For example I regularly press a/i/o before I start typing the text. Or I try to block mark/yank text selections, etc. instead of use copy and paste :)
After a few weeks of regular usage you start getting a grasp on vim and will constantly ask yourself why all the other editors suck :)
(I tend to use console vim - not macvim. Macvim somehow doesn't feel right.)
I hate to lead this further off-topic, but I'm trying to get into Vim myself -- how to you approach having multiple files open? Buffers? Tabs? Windows? The netbeans/visual studio/et. al. tabbed approach has always worked well for me, and I'm finding that to be my biggest stumbling block in switching to Vim.
Try the MiniBufExplorer plugin. It gives you a list of all open files in a different buffer, and you can switch to any of them by just moving into that buffer and pressing enter while on the filename.
I use splits and vertical splits. Tabs are an option too, but I usually don't leave that many files open at once.
For browsing files inside vim I use NERDTree (or if I remember the filename :e <filename>). To quickly open the file's headerfile I use http://www.vim.org/scripts/script.php?script_id=31 - it takes only a :AS to open the file's header file (vice versa) in a new split. (Hint: Map a key to next split/window to switch fast between them. I remapped F1 for this purpose.)
If I really need to have many files open I just open a new tab/window in my terminal emulator. (There are also tabs in vim but I had not a chance to get used to the tab commands yet. gvim/macvim offer more abstract tab support - the tabs are real vim tabs but they are represented as UI tabs. So you can still yank/paste between them but have a more Visual Studio'ish feeling.)