Here's the cursor I use:
I find the black outline makes it easier to see when it happens to be over blocks of bright text. Also note that the hot spot (where the mouse click is registered) is located where the black lines cross in the original cursor because that cursor was intended to be used on a white background, so the white lines in the cursor above are all where the original black lines were.
Still hard to believe Apple has a "Dusk" theme as their second color theme and yet they never bothered to change the ibeam to work on that theme. Then again, I never had a huge problem with it until we moved and I now sit in front of a bright window that makes my screen appear dimmer and the default ibeam much harder to see.
Yes, I like your cursor better, except it is only 16x16 pixels while mine is twice the size. I had to expand yours to 32x32 and it is working well. I also notice that in Preferences there is a Cursor color option, however that only affects the Insertion Point flashing bar, not the cursor. Apple really does some dumb stuff sometimes.
I checked out the Dusk theme which has a dark background, but I use Midnight which is totally black. I also have the Thunderbolt display at size 2048x1152, possibly Xcode knows it and that is why my cursor is twice the size of yours. Unless the Midnight theme selects large fonts and cursor, don't know. I am using Xcode 4.4 in OSX 10.8.