This game, or more accurately, simulator, is one of the best games I have played in a VERY long time. No matter what your taste in aircraft or flying may be, there is fun to be had in DCS.
You can purchase aircraft from a wide number of time periods, from WWII, The Korean War, and even modern battlefields. There's also some very nice helicopters to purchase, but I can't comment on those, as I don't have any.. ;-;
If you like CAS, BVR, Dogfighting or just screwing around with friends in fast aircraft, DCS World is most certainly worth trying. The free aircraft you get, the SU-25T and TF-51 give you a pretty good feel for what you can expect in DCS, but I definitely reccomend picking up a full fidelty module if you like it, great fun learning what all the alarms mean... ._.
One quick note though, getting the game directly from the developers is a better choice than Steam, as the version from ED's site gives you earlier access to new modules, updates, and let's you buy modules from sales on ED's site AND Steam, which cannot be done with the Steam version ;D
tl;dr : BUY IT AND YOU CAN CRASH TOO :D