I'd like to try to build the latest QT source from the git repo; I'm running openSUSE 11.2 with KDE 4.4 (QT 4.6). Are there any issues to be aware of in this case? I'd like the system QT libs to remain and be used by the system software, but use the newer QT for apps I build from source (rekonq, etc).

None that I am aware of since this is what I do myself without issue.

Note that it is better to use a version specific branch of Qt, eg: 4.6 or 4.7 instead of master.

Simply ensure that PATH and LD_LIBRARY_PATH are set to include your new Qt directory first and it should work fine. If compiling applications you may also wish to set CMAKE_PREFIX_PATH and PKG_CONFIG_PATH.

I recommend using the same Qt version to run all of your desktop apps ( as Qt is binary compatible, no sense in having multiple versions loaded at once ) so I set these vars in ~/.xinitrc before running startkde.