Seriously consider if you need to upgrade to 5.5 before doing so
It is brutally slow. We're being told 3000 clients is on the high end of their scalability, because we use Smart Labels with wildcards, and run a few scripts every couple hours, that's a lot of the cause of our slowness. Everything worked terrifically in 5.4. Just as a warning, seriously consider if you need any of the features of 5.5 before upgrading at this point.