I've always really liked Weber's game and believe he's been the single most consistent d-man in the league for the last five years slightly ahead of Duncan Keith, which is a huge plus for him. Weber has unfortunately never won any hardware as a defenseman, but in terms of abilities on the ice, despite being a vastly different player than Subban and having different strengths, I believe they are both of roughly equal quality.
I also believe that, as of now, with the makeup of our team as it is, Weber's more defense-oriented game MIGHT be a better fit considering our emphasis on team-defense and dump-and-chase philosophy.
Staying as objective as possible, I can reasonably fathom Weber having a bigger positive impact on our team for the next 4 to 5 years if he doesn't regress, which might have been our GM's aim in this trade (as well as accomodating Subban's wishes maybe).
My only immediate concern with Weber pertains to how / if he will embrace the city and our team and play up to his own very high standard. I worry a bit about how he might react to having been traded to our hockey-mad, rabid, media-driven pressure-cooker of a city. Nevertheless, with what I've seen of him on the ice and in his interviews as well as from the professionalism he seems to exude, he should fine.
HOWEVER, trading a guy of Subban's stature, a true franchise defenseman, for an older guy is really, really, really not the smart thing to do in spite of a potential better fit. In Subban's case, I can reasonably see another 8-10 years of very high-level play while in Weber's case I believe it is closer to 5 or 6, making for a difference of about 4 years.
Let's face it, as far as top-level franchise defensemen go, the single most important thing teams should keep in mind is their age and the time they've got left to play as their impact on the ice is so great and far-ranging that their very presence opens or closes a cup window (just ask Edmonton fans about the importance of top-end defensemen).
As such, that aforementioned difference in projected longevity makes this trade very bad for the Canadiens, even with a possible better fit of Weber on our team.
Anyways, good or bad, I accept reality and make peace with this trade which brought a defensive stud into our lineup at the expense of another. In the end, I look to next season with an open heart ready to welcome Weber into the fold and, like with Subban, cheer for him and the team like mad.