I was playing Allods Online (from mid summer 2010 to February of this year), I got bored and I quit. I played many games in between until my latest preferred F2P MMORPG being Champions Online, it's a very solid game, I like it and I like the creativity of some people out there with their very unique characters and fleshed out bio. There's also some role-play thrown here and there (Club Caprice mostly) and it's fun. The missions are diverse, not much grinding, and not as character level-dependent of a game than Allods Online was, so in Champions Online I can often take on foes of three or four levels above me, one at a time that is but it can be done. I like that, it's risks I can take if I feel like it and not a guaranteed death if I'm careful.
Champions Online has evolved quite well since I first played it about three months ago, there's regular updates and its current status now is quite better than it was when I played it back then. I've tried many other F2P MMORPGs out there and so far Champions Online is my favorite of the bunch. Last but not least, Champions Online can be played solo from start to finish, as far as I know. There's only a few number of bosses that occasionally spawn from quests or just some non-quest tough bosses that need to be killed in a party, but other than that pretty much all the rest can be solo'ed. That way I don't have to look around for "properly balanced" parties to completed quests and I can play it all on my own as casual as I want if necessary.