I really like the idea of the E campaigns. It almost feels like the books we read. In those you rarely see the inexperienced PC become the uber-God-like PC. I just wish I could convince someone to do it.
I, obviously, haven't done it nor do I truly know much about it, but I would think it would be great, even in the long run. After all, while you gain feats quicker in E than levels in D&D, leveling in standard D&D makes you far more powerful, doesn't it? Also, some feats that you would like to have in D&D but don't take in favor of more optimized feats, you can now take. Sort of rounds out a character, IMO.