I think the knocks on him are size (under 5'10, 195 lb - but whattayawant, he's a safety...) and on-field "off field" issues, i.e., character/maturity. Unfortunately for Merriweather, most people remember him for swinging his helmet around at other players during the Miami Melee. You don't think that makes you pull some game tapes, and see if he's a little on the emotional side? Start looking real hard at pouting, or disagreements w/coaches on sidelines? In other words, you vet the choice, and figure out whether the outburst -- or taking part in the mass outburst -- was an aberration, or whether he's "just that kinda guy."
Hey, Sean Taylor was a much more highly-touted safety coming out of college than Merriweather... would you want him?
What we know: Merriweather had a moment of madness. What we don't know, and maybe BB/SP et al. are currently finding out: uh, does he get in scrapes in night clubs? Does he carry a gun? Any reputation for substance abuse? Etc.
One thing is certain -- if Merriweather had put himself in the middle of that scrum and tried to contain a guy or two, the NFL personnel planning draft selections would be saying "that is a man."
I know that's demanding something way past most kids in an us vs. them mob scene. But being the guy swinging his helmet does not translate to leadership on an NFL level - at least the way the Pats play the game.
Just edited to say: but its a good sign they've worked him out twice now, if I remember correctly... like us, they have to be salivating over the versatility. Hey, if they trust him (say, at 28...) so do I. Hell, they might even get him in the 2nd round, if they pull something to move their second rounder up a few notches.
PFnV