How about making OS X even easier to lock down for corporations, schools, etc.? It's still not there - especially for those of us who have LDAP set up. Lots of small hacks must take place so that the preferences of the default local user can stick to our LDAP login users. Also, Apple needs to fix the bug that causes the dreaded "hdiutil: convert failed - image/device too large" problem that's plagued Disk Utility ever since 10.3.9 (it worked correctly in 10.3.8 and earlier). Just my $0.02, from an IT perspective.
How Could OS X Be Improved?