I use Trillian as my primary client, and have been for a while. Their newest builds sync all of my chats across protocols across clients, which is nice as I frequently switch between my Mac and PC for various things and it's nice to have my chats all sync'd

Not me. Trillian's iOS IM client is one of the few that's any good.

Indeed, especially if you use it in combination with their desktop applications (win or mac), because the "continuous client" functionality makes switching between devices fluid.

Definitely. I wish Apple would have bought them instead of rolling their own iMessages. Trillian consistently delivers messages to me wherever I am, and keeps everything property synchronized better than any other messaging tool I've used.

the windows client is equally excellent, and it's still the only IM platform (to my knowledge) that supports inline image sending, which I've gotten very used to. Plus the windows version handles IRC elegantly enough.

The screenshot function is quite a handy tool too.

I was (having long abandoned it), and I still use ICQ on Pidgin

Honestly if you use gtalk/hangouts you'd be crazy not to use Trillian. It's far more intuitive and user friendly.

That's exactly what I was thinking!