I had been under the impression that it was likely to be safe to use 
'epel' packages, so, wishing to provide feedback, I installed a new 
version of qtwebkit from epel-testing.  No hint of problems during 
installation, but programs using it failed.  I now have them apparently 
working after installing glib2 from SL7rolling in place of the earlier 
build in SL7x, but I'm less than happy about such cherry-picking.

I'm told that epel packages support the current upstream release, 7.1, 
so it seems to me that systems based on the recommended SL7x and using 
epel will be at risk.

https://bugzilla.redhat.com/show_bug.cgi?id=1202735