For anyone sitting on the fence, jump in! Its awesome. Incredibly detailed so be prepared to spend some time to learn the systems etc before you can go full on into combat! The main manual is currently around 700 pages long, but as always you dont have to learn everything straight away. There are multiplayer servers.
Yes it is the full game you will buy but the game isnt a release copy yet. They have allowed pre-purchasers access to the Beta. I'd say around 85% of it is currently finished, with updates supposedly being released every 2 weeks. If you buy into the Beta now you WILL have the release copy of the sim later.
Missing items (ie the remaining 15%) currently include things such as air-air refueling, ATC comms, multi screen support, further missions, more detailed scenery, slight tweaks to cockpit systems, 64bit TrackIR support and no doubt plenty more!
The training missions are currently a little buggy but nothing too drastic, just remember to pause until you have properly digested the on screen text. Keep an eye out for Matt Wagners producers notes on youtube. Currently there is only the 2 part engine startup video. The ones he did for DCS Black Shark were VERY helpful in learning the aircraft systems and usage. Oh and dont be phased by that video, it is drawn out because he explains it, once youve done it a few times you'll be in the air v quickly and will still be switching half the stuff on whilst in the climbout!
In all, its brilliant and is set to take over from Falcon 4.0 as being the definitive hardcore flightsim.
I will add that TrackIR is very helpful and once youve used it you wont ever want to fly any sim again without it.