Most of it isn't a big grind. If you arent wanting to 1000G this then it isnt too bad. I quite enjoyed the game up until the end and got 750G from it. The last 250G is 5x50G for maxing classes (which is, admittedly, a HUMUNGOUS grind. I'm not willing to do this!)
Strangely enough this is actually the type of game where it is possible (although highly unlikely) to complete it without getting a single achievement.
Max GS XBox:
SEGA Mega Drive Ultimate Collection / Halo: Reach (Pre-DLC) / Beyond Good & Evil HD / Alan Wake (Pre-DLC) / Bastion
Max GS GfWL:
Dark Souls / Halo 2 / Viva Piņata / Fallout 3 / Toy Soldiers