what did surge do?
It increased attack speed and ability power. Also you're size.
I'm pretty sure the intention was to offer an offensive bonus that was roughly equal in power if you were AD or AP, but most people just saw it as wasting a lot of potential unless you could use both the AS and AP aspects.
It wasn't that bad on marksman for burning down a tower when nobody was looking, the AS was actually pretty solid.
Also really amusing on a Cho'Gath with an allied Lulu. Get enlarged with max feast stacks, pop surge, can't see anything on your screen but Cho'Gath.