Nothing wrong with a flat, one plane swing as long as you are using your big muscles correctly. My swing is uber flat like a Kuchar, Dufner, and Hogan.
Has anyone tried a putting grip like Stricker? Basically a fully unhinged left wrist, resulting in a shaft angle that approaches 90 degrees to the ground? It dramatically reduces the effective hitting area because the heel comes off the ground so much but wow, it really kills off side spin on putts. I know having a shaft angle that is 90 degrees to the putter head is illegal and now I can see why.
I'm guessing the major downside is you have a reduced area to place your mishits, after which it's a straight shank? I don't know... I've been using this grip for a couple days now and am really impressed with the result.
Also, someone a while back mentioned struggling with distance control and thought about buying a bigger head to help. Isn't that the opposite of what you should do? Smaller, lighter means better distance control (better feel for the clubhead), bigger, heavier means better line/aim control (clubhead won't twist, easier for straight back, straight through)?