I saw mention in other topics that there were a few servers still online, question being is anyone playing though?
I'd be tempted to pick this up just for the multiplayer.

From what I've seen, you can find a handful of people online. Most servers are empty though.
(Mind you, I only looked once, two months ago, so I don't know how representative that is.)
Screenshot here.

I logged in and joined a server with 1 guy in it... and he's obviously one of those people whose been playing painkiller since day 1.. i was decimated... i'll probably try online again but there better be some noobs out there :P

There is a post in General Discussion about a GOG gaming night, perhaps post in that thread to see if anyone else is interested.

What post would that be? I would love to play this game GOG gamers. It is mad fun online and no one is on except maybe 20 people.

Here.