I don't really think it's that necessary to simulate a real cube, though. There are really three steps in speedsolving, that you do over and over: finding pieces, figuring out what turns to do, and then executing those turns. You can practice the first two pretty well by doing computer cubes. As for executing the turns you want to do, you're right, you can never learn that from computer puzzles. But if you can do turns quickly on a 5x5 you will be able to do them on a 6x6 or 7x7 too - it's the same principle, with just a few more slices. I think once you try the 7x7 you'll find it feels pretty similar to a 5x5, just with more slices in it and more roundedness. As long as you can find pieces and figure out what turns to do, I think you'll get some really good times on the V-cube.
