Oh, man...
My very first 3rd edition character (starting about a month before the PH came, courtesy of leaked rules) is pretty much the standard in our group for (1) why you should never play a bard and (2) how NOT to multi-class. Her class breakdown when the campaign was terminated Bard 7/Cleric 4/Herald 5/+1 ECL for being a variant tiefling (-2 Str, +2 Int and Cha). Herald was a prestige class from a Dragon that's basically a secret agent class -- sneak attack, permenant nondetection, the ability to fake out alignment detection, etc. More importantly, it had its own casting progression, including some unique spells (one of which at the time was a 1d4+1 Cha boosting spell).
So basically, the poor girl was tri-classed in three different spellcasting classes. As direct result of this, she was completely ineffective in actual combat, and also completely overshadowed by the other three spellcasters as a support character. Between that abd the DM deciding that a +68 on a Diplomacy check (which she would've been capable of by the time she reached 9th as a Herald) would never even compare to a first level wizard casting Charm Person, she was pretty much the most useless character ever.
So how multi-classing is done nowadays is as follows:
1) Multi between core non-caster classes is actually pretty well expected. My dwarf in the current game is taking exactly 2 levels of fighter, ever, pretty much just to ensure getting Great Cleave.
2) Multi between caster and non-caster generally isn't done, unless necessary to fulfill a pre-req for a prestige class. The exception to this seems to be for 1 level wonders (such as the cleric with a single level of monk). Our characters that are already multi-classed (we're only 5th level) are the cleric that I already mentioned and the rogue1/Sorc4 (the party "bard;" general consensus in the group is that a rog/sorc could easily do anything a bard could do better).
3) Multi-between spell-casting classes is never done. Unless there's been a character that I'm unaware of, my bard is only 3e character anyone has played in our group that took that route.
4) Prestige classes... the "bard" and the druid have actually written up their characters with a prestige class already in mind (virtuouso (mispelled I'm sure) and elemental archon or something like that, respectively). I simply wrote myself a prestige class that my dwarf can't meet the pre-reqs for until 10th level. I think the cleric has also written up his own prestige class. The versed warrior (an R5P core class) is starting Purple Dragon Knight next level, and then going into Field General (R5P presitge class). He was originally going to take Warmaster, but I talked him out of it. The hat-caster (very weird class; gets to custom build a spell-list from the wizard, druid, and cleric lists, but gets less spells per day than a wizard) is currently debating whether to just abandon his class altogether and set himself up for Rage Mage, which would actually make him the 2nd character ever to have 2 spell-casting classes.
In short, not only do people take prestige classes, you're basically considered an idiot if you don't take one. Paladin and Monk are the only classes where sticking with the core class proper is actually worth it; with the rest, you should multi into a PrC ASAP (though it'd better continue your spell progression). Hooray for power-gaming.
We have yet for a campaign to actually REACH epic from low levels. Most of us may well just work out our prestige classes as epic classes and keep right on taking them.
