[ZPinhead]

Based on my experiences last year, if you're only playing in one prelim event, I would definitely pre-register (and will be). It gives the peace of mind knowing that you won't end up being an alternate (or locked out entirely) and you can avoid having to stand in line at the cage (there's a special podium for pre-registered folks).

On the other hand, if I was planning on being in LV for a couple of weeks and playing several events, I would probably not pre-register. That way I would have more flexibility to change things around depending on how I finished/cashed.