I think the major problems were that there was nothing about the 2004 version to justify the upgrade from 2003 or earlier.
About the only useful tool these days in SystemWorks is SpeedDisk, and honestly... The amount of time you spend defragmenting your disk probably far outweighs any performance gains you might achieve. And with AVG Free being a far superior anti-virus program (that's free I might add), you don't need it for Norton Anti-Virus either.
Personally... I'd skip SystemWorks alltogether. Use AVG free for all AV needs, XP's built in defragmenter is Good Enough(tm) if you decide you really need to defragment... NTFS has enough journaling features that you don't need tools like scan disk. In my experience the recycle bin overlay program causes nothing but problems, so what else is left? GoBack? Just a version of System Restore already in XP. Save your money, spend it on something useful or entertaining.
I believe there were horror stories about SystenWorks 2004 and Win XP. Now I see that SW 2005 is out. Has there been any major problems between this new version and Win XP Pro SP-2?