Always Multiclass!
Cool, interesting thread! I multiclass, without fail, and usually with three (or more!) classes. I know that it goes back to my HERO gaming roots, where you build your own very specific character conception. The flexibility added in 3E (and ESPECIALLY with the new Complete class books in 3.5E) make it very possible to essentially point-build characters for d20. For example, in one campaign I play a Druid- but, he came from a norse-like barbarian tribe, so I gave him a couple levels of Barbarian; and, to act as the party tracker, it made sense to add a Ranger level which fits the conception, too. For the most part (except Cleric) core classes are balanced enough that mixing and matching works just fine IMO. It does suck to multiclass with spellcasters, though, even with feats like Practiced Spellcaster helping make it possible. I also like the idea behind several Complete Adventurer feats that allow class-combo characters to continue to grow their base class abilities. For me, I just think it is more fun to design the precise character that you want to play, rather than just the core class at face-value, although feats do help define characters as well.