I once build a Rectangular Tile engine on the forms GDI surface while flipping it using BitBLT... If you read the tutorial on DelphiGamer I take it that you read my tutorial on the subject!

It can be done, however you need to realize that this is never going to be as fast as a DirectX / SDL application, so you'll have to leave stuff out or program speed-efficient, however the fact is that some things just cannot be done on the GDI surface... It's a nice surface to work on though, I used it in one of my chess games to make it compatible for NT4 machines and it worked without a problem, however a chess game isn't HUGE on graphics...