my 'experience' isn't so good. I have a pretty standard oldish system right now. No slouch for most games, but all the newer ones e.g BF4, Crysis 3, FC3, COD Ghosts are too demanding for my system. I have to dial back settings in those games I mentioned to medium and at a res of 1680 x 1050 so that I can hit between 40-60fps whilst playing.
However Geforce experience, thinks my Q6600 and GTX560ti combo are an I5 4570k and a GTX780ti, judging by the 'recommended settings'. Suffice to say, playing at those settings makes the games unplayable on my machine.
Ultra setting my rear end. I would say set up each game yourself.
I personally have mixed feelings about the software, on one hand it finds quite a few games to optimize (no issues with a 650ti), and searches for driver updates that I would otherwise miss. On the other hand though, when updating the driver Geforce Experience is constantly freezing at some point during the download or installation of the driver.