The only guilty gear game I played was Isuka. I had never played it before, and I beat someone who had practiced all of the fancy combos and roman cancels and whatnot using potempkin whilst button mashing.

I liked the music and the character designs and the general sense of humor but I hated the manual switch, the background jumping, and in general playing the game.

I've heard Isuka was a weak entry in the series, so I will eventually give another a try.