He started off as a really great character.
He is very much based off of Miracleman, so that's probably the biggest criticism about the character. I wouldn't say he's an outright ripoff, but it's very obvious that he was a major influence. When I first heard of and read the first Paul Jenkins series I had no idea what Miracleman was, so I thought I was reading something incredibly different and new. Turned out it's the opposite, but it's still a good story.
The second Jenkins series with John Romita Jr. is absolutely terrible. It's like the wanted to make a new miniseries because Bendis was re-introducing him in New Avengers and asked Paul Jenkins to write a new story and he had no ideas except to turn him into a drug addict. It was a profoundly disappointing series, and that's an understatement.
Then came his appearances in New Avengers...I actually kind of liked it at first for the most part, even though, looking back, the stories weren't very good. But they quickly got really bad, and it became clear that Bendis hadn't the foggiest idea a) how to write the character or b) what to do with him. It got worse and worse, until he got turned into Norman Osborn's lap dog.
Other than all of that, there is a pretty wonderful 6-issues mini written by Jeff Parker called "Age of the Sentry" that would have made an EXCELLENT immediate followup to the original (first) Jenkins series, if only we could forget that the second Jenkins series and all of the Bendis Avengers stuff existed.
