Might be the best mecha game out there. For now...
On first run of the game, it won't be that difficult. The missions will be moderately easy and some will be moderately difficult. But you won't have problems finishing the game for the first run. Then, you can play the game over and over again to challenge all difficulties and get as much fund as possible to gear up your NEXT. Sounds pretty easy, but it will be very time consuming. And once you purchase all parts, it will also be a trial and error to get the best NEXT you like. You will have to assemble it, try it out, change parts, change generators, change weapons, and a lot other things. And yes, it is very realistic and very difficult to actually get NEXT that you really love. Usually after playing some times, you will decide that your NEXT needs this and that and you will have to customize it again. This is not a game for easy gamer, because you really need the time to master this game. Once you are ready and done with the offline story mode (that has alternative endings and you can choose which military factions you will support), you can go ahead and challenge other players in online mode.
Graphical quality is great, might be able to be better, but I am not sure. It is seamlessly integrated with gameplay, so there is no problem with it. Loading time sometimes becomes an issue, specially if you are not on a mission and just want to try your NEXT. Faster loading time would boost this game's rating.
Overall, if you are looking for cool, fast-paced, thrilling mecha game, you are looking at it right now.