I think it might be handy to have a sticky topic here for known issues with 2.5 as a quick reference.
I will update this first post as new ones are found and try to remove old cleared issues.
Myself and SG have noticed a certain amount of lag-moments, with no as yet obvious causes.
Had a game crash when messing with the in-game troop transport feature, which itself seems buggy.
Have repeated DCS freezing of some sort when I am trying to edit the Av-8b controls when out of missions (not from in game menu) and have to alt/cntrl/del to get out of this.
MP issues. As SG also states below, I too have had mixed fortunes joining MP. 1st attempt to a server with 15 was aborted as it froze in attempt. Next I joind a sever with only me and it was easy to get in etc.
Had issues trying to join MP tonight with protection -I only have squad-skins and it's telling me only pure game allowed...
Issue with late activation units; in MP only AFAIK, and it doesn't seem to affect the server, only clients, you can't see anything not activated. Also with static ground vehicle objects in MP you can't see anything ticked in the ME as 'hidden' -it makes them invisible in game! I placed structures and a helicopter with ground vehicles, and it was only the vehicles affected.