The offered here at Amazon Download version is nothing more than the actual DVD version that you can download. But you have not even the version here from Amazon Download, you just take the keys for the game that are provided by Amazon and logs on to Rockstar and the game can be downloaded there. As has already warned you need enough memory on the hard drive, both a halfway reasonable PC. Rockstar really could something more screws on the performance, because even with strong PCs neither the CPU is still busy, the graphics card perfectly and it is a lot of power away.
Control with mouse and keyboard works quite well. Some keys have been chosen somewhat unfortunate in my opinion, that can be fully customize everything. But who can live without it, of course, playing with a controller that works beautifully. The flying and driving, I find the controller maybe even a little easier - have tested it with the DualShock 4 on the PC.