are their any tecnical issues with this hack? (such as the messed up fade effect when moving from room to room)

Yes.

The original GameBoy relied on adjusting the tiles during the vblank cycle. It would "freeze" the game screen, and during that freeze would slowly "fade out" that still image while the game cleverely and invisibly switched tilesets from room to room. GBColorizer's current incarnation inserts its color palette during vblank cycles, which means that operations which would ordinarily occur during vblank are bypassed. This results in the aforementioned garbled look during room fades, as well as the loss of "pulsating" item effects. The Metroid Queen relies on that vblank cycle to erase the previous position of the monster; since that vblank cycle is bypassed, you end up with a garbled mess wherever the Queen moves. This is a limitation of the GBColorizer program, again, and I'm not aware of a way it could be solved (with the exception of going into the ROM code after the hack was applied and fixing the vblank code).