Seriously though, David basically summarized it for you .. If you feel your 350D is a limiting factor to your photography, then upgrade is the only solution (it will boost your moral of having a better camera but not your creativity). Of course, if you are not happy with the ergonomics of 350D, go do the upgrade (it is still a justification).
I am shooting with a 3-year 10D, and I find that the bad pictures that came out of it is usually "operator issue" ..
Actually, if you asked this question, then you don't need the upgrade. Those who really need the upgrade will know that they need it and they will just do it. So in short, you don't need it. but by all means buy the 30D if you have the money to spare and feel happy about it.
What is stopping you from buying either one of these cameras? Buy the 30D and you will not regret but then if $$ is an issue, then buy the 350D. Simple. :sticktong