Wasn't too bad, though I only played on Sarlona (the 'roleplay' server, as in, it has some roleplay guilds and permadeath guilds), and even then only with people I knew.
Played a cleric, then favoured soul, both times I had to have the party invites option turned off otherwise it'd be constant request popups, often from the same person.
I gave it a fair go, over a period of a bunch of months, but I never reached 20 and I hear there's a bunch more interesting stuff up there. Lag gets bad, though (as in on some of the final quests, as a cleric your job is to tap the 'mass heal' spell every 10 seconds, as the damage being dealt by everyone causes such a lag spike that no-one appears to move until the monster dies, or the party wipes. No exaggeration).
I only gave it a go because of a thread here which was about favorite gameworlds - Moloch gently implied that a lot of the forgotten realms supporters were fanboys without enough experience of other gameworlds to defend it. Moloch was right, as he usually is :P So I went to try Eberron, or 'Final Fantasy and Dragons'!
Still a Realms fanboy, only now more educated :D