This RPG is awesome! I've tried a lot of games and have always scurried back to D&D 3.5 or Pathfinder. Lords of Gossamer and Shadow is an amazing game that needs more exposure. I never played Amber and wouldn't be able to compare, but because of LoGS, I wish I had known about Amber in its hay day. The diceless rule set will be a hard sell for some that will think the game is completely arbitrary. If you/they can get over that mental hurtle, you'll find a RPG full of infinite possibilities that won't become a headache because of having the crunch rules and mechanisms.
Lords of Gossamer and Shadow is definitely a RPG that will flourish in play-by-post forums. I don't know how well I would a game like this in person, but I have been running a fairly interesting pbp group on RPGpost.com and I think I have 3 players that are just as hooked as I am on this game.
I look forward to supplementary books for the system, but I just don't know how they could improve it.
[5 of 5 Stars!]