GDB 6.4 has just been released.  See http://sourceware.org/gdb/news/

Attached is a version of gdb-ui.el that works with this version and should
perform better than the one currently in the Emacs CVS repository.  I've not
committed it yet because I want something more general as a first release.

Here are some of the improvements:

1) Watch expressions (arrays, structures) update more quickly.
2) Emacs identifies which buffers contain source for the debugging session
   much more quickly (Stefan's gripe).
3) The locals buffer provides information about type.
4) Register values which change are highlighted in the registers buffer.
5) The mode uses more GDB/MI commands which should help with future proofing.

If you find it doesn't work, please tell me.

Nick