I tested it with Magical Tetris Challenge (PAL, as the game was never released in US), and it works perfectly.If you want to try, here is a experimental build with a "Force NTSC" option. It allows you to run PAL games at 60hz without any patches.
It seems to work alright.
The PAL version was poorly converted to 50Hz (from the JAP), making the game 17% slower.
I suppose it will for "native" 50Hz games (i.e. european games developped in 50Hz). Colin Mc Rae 2 is notorious for this, as the NTSC version is a crappy 60Hz conversion from the PAL version. Yeah, for once, the NTSC version is an inferior here. ^^Some games will run faster than intended.