I think I've been very lucky with my server-finding - I actually once found a really good public server. The admins were all active, there were very few restrictions on items / blocks, lag wasn't too bad usually, the community was somehow really good despite being public - probably due to the regulars almost all being awesome - and there was no world limit.I would add to the list of major reasons why I never play public-server SMP:
1. Seems like half the modpack items are banned
2. The "infinite" world has a finite border around it
3. Must break each block twice before it breaks once (lag)
It never fails. I finally found a server that didn't have problems #1 and #3... but my boat crossed the hidden border (problem #2) which I didn't know about, and the game killed me when I did. I never went back. To heck with public SMP servers, they all stink. (I'm being polite with my words)
And that was the only server that was half as good as that that I ever found. Sadly such places are rare these days - it shut down a while ago, after going through countless changes to the modpack and whatnot.