Has anyone tried this on multiplayer yet? I tired the other day, but everyone playing was on version 1.96 (GOTY Edition) so I couldn't join any games. Hopefully there'll be some 1.99 servers setup.

Nowadays there are some servers, sometimes even populated ones if you're lucky. Had some fun last night, so have a look in the weekends :)

Ive had the same experience....ther are alot of people playing operation flashpoint 1.96 especially in europe....now that ive switched to ArmA (which is version 1.99) there arent as many people but there are a few servers...the established players seemed to be staying with 1.96 for now mainly because its what they are used to......easiest way to get started is to start a co-op game yourself (ping ddoesnt matter so much in co op) and people will join....its surprising how fun this game is online..its not a run and gun game so dont go into it like it was counter strike source...work with your co-op players, use the terrain..find a good sniper rifle.....one recent game i was in a co-op server with one other player..couldn't for the life of me figure out where he was until i spotted something on a high hill with by binoculars about 1 km away....i got to his position wan we began to snipe a russian camp from distance...

I just bought it this weeks sale. I am wondering how long it takes for GoG to send a CD Key so a person can play MP/LAN?

My GOG game works without a key. At least I was able to join in some MP games (I did not try LAN). I hope I am not screwed by activating the gameplay degrading software!
:(