Jeph Loeb is one of those creators that are hit and miss, Superman for All Seasons is one of my favorite comics of all time, period. However, other titles he's written have not been as good. Some, such as what I've heard about his time on Ultimatum and The Ultimates have been not so good.
I was excited to see him working on Heroes and Lost. He also worked on Smallville.
I give him the benefit of the doubt, usually. There are some who view him as a "Midas in Reverse" thinking everything he touches turns to crap. I take each work of his on its own. I'll admit to liking Ultimate Spider-Man, but sometimes the show gets exasperating.