I use 2x normal experience in my home game, and it works great. The world has a more high-magic feel since you hand out twice as many items for each set of encounters, but I'm fine with that. (The players are just hitting Leve 9 - I forgot to double the magic items for the first few levels, then noticed they were getting seriously behind and started keeping closer track of how many I gave out.)
The only complication I can see is that, in my home games it's easy to sit down whenever the players are about to gain a level and work out how many magic items they should have, and add some more to the next encounter if they're behind. In L4E, where a single DM doesn't control the characters for a whole level, it would be harder to keep track. We may need some way to top of characters who get behind the curve. (But we can always add that later if it turns out to be a problem.)