It's always difficult when a band with such a good, well-known, etc. frontperson has to get a new one. Sometimes it's successful (i.e. AC/DC with Brian Johnson is just as good as Bon Scott, Iron Maiden with Bruce Dickinson is thought superior to Blaze Bayley), but a lot of times it fails (i.e. the Motley Crue album with John Corabi was a STELLAR album, but Crab wasn't Vince Neil so it flopped. If it had been released with a name other than Motley Crue, it would have dominated.)
Then you have the case of Van Halen. I personally prefer VanHagar over VanRoth because I think Hagar is more musically talented (he's a better singer and can play guitar) but Roth is the more dynamic stage performer.
Good to hear AiC still has the magic.