Zoomers - BlackHawk - Howthe and many others had deplomacy's first 5v5 all human game, from everones point of view, it was very disspointing.
Benefits to Deplomacy for online
- FFA is much more better
- New Weapons, Amour Pacts etc
- Envoys grant bonouses
- Faster Option for Credits and other options (culture etc.)
- Better Pirates
Drawbacks
- Have to research to feed people
This is very bad as we all know that this game aint perfect in map layouts, so if an member of your team has no asteriod, was badly placed on the map or between two people and many other situations which it is vital to feed early to that player for his survival, he might as well be as good as dead. Researching to feed players online is not a good idea, as all it takes is for one person to be map f**ked for the game to quickly turn to 4v5.
- Deplomatic Victory
What is the point in using this? in a game with locked teams? so instead of fighting each other, we just spam envoy ships until we have enough point to win the game. For FFA yes! not for locked team games.
- The AI
For some reason the AI offline is amazingly better in this version or expansion of the game, but in multiplayer, they still suck hard once an human player has left (either by disconnect or minidump), there just too easy to pushover after that.
many more but I am in lecture, need to listen 
Short Conclusion
Should people buy this game for MP?
Yes if your playing FFA and play againest the AI, or love playing single player
No, if you like playing with restriction on feed till researched.
I would buy this game for single player, and online FFA or Comp Bash. But not to play 5v5 or other similar games aginest all human players, it just aint worth the hassle. A few new wapon, armour upgrades etc (pacts) aint worth it for multiplayer. Because of the problems caused by map layouts, feed is needed at a very early stage of the game, and sometimes waiting to get the technology up, aint good enough either.
The only postive thing is the new faster options for the game, but there are more drawbacks to playing this game online, than offline.
My Ansewer? Stick with entrechment, and buy deplomacy for offline play or ffa online games only.