I just LED'd my Lethal Weapon about a year ago. Overall, it looks great, but there are times when it's a bit too much. For example, when ALL the GI (playfield AND backbox) flash when multiball is ready, it is a bit seizure-inducing if you're playing in a dark room. I've got a plan to fix that, but I've loaned the machine to a buddy, so I cant try it right now.
Just keep it in mind. I'd think about leaving some of the backbox GI incandescent so the bulbs don't do such a sharp ON/OFF when they're flashing, but that's just me.
Jeff