I bought a G400 (basically MX518) and was bit worried about the "angle snapping" thing but it doesn't seem to do anything, not that I notice. I replaced my G9 with the G400 (G9 don't have the snapping, although the G9x does by default) and IMO the G400 is definately better. I play at low sens so it's probably the fact that opticals are better for tracking than lasers (which is why I bought it) the G9 skipped all over the place when moving fast on low sens, so I couldn't be happier with the G400.
The shape still feels weird to me compared to the G9 but I'm getting used to it.
I'd definately recommend it to anyone looking to buy new mouse and is a low sens player.