I'm still not too happy about our players at this position, either.
Bigby is starting to look more and more like a one year wonder. He hasn't been showing us those big hits and that ball hogging skill that he showed at the end of the 2007 season (and a bit at the start of 2008). Right now, he's a LB/S tweener who's a slight liability in coverage. I hope that he'll play well in this 3-4. Maybe Capers can utilize his aggresiveness a bit better.
As for depth, I'm not too convinced. Smith seems ok, as long as he doesn't say or do dumb things. I don't want to see him get burned like he did in Pittsburgh.
I don't know what happend to Rouse. He was a PH.com favorite last year. He did have a nice pick in that Colts game last year and he might benefit from this 3-4, but he should just start following the play more and the QBs eyes etc. less. He seemed to be hanging with the QBs eyes a lot last year. It got us a interception in that Colts game, but it can be quite disastrous.
Peprah and Bush should be burried in the depth chart and stick to ST, mainly.
Collins has just been great. He's not that much of a big hitter and he's no Ed Reed (just yet), but he was very good last year, without any pressure on the QB. I can't imagine how good a (statistical) season he can have this year. I can see him playing deep in cover 1 from time to time and pick it off with his great hands and speed while the QB gets some pressure in his face.