I miss Portnoy, of course I do, but that doesn't mean that I don't think that the band is ultimately better off with Mangini. Old Mike was usually the center of attention, both on and off the stage. New Mike is still a fun guy but from what we've seen so far he's more... mature, and I think that suits the other members.
This is a tough question really, Portnoy did so much for this band but a lot of us would argue that he was the main reason the band took more than just a couple of steps in a direction that a lot of us would consider to be "wrong" in terms of what kind of music they put out. I love his drumming and I'd still say that he's one of my favorite drummers of all time. To me it's more than just clear that Mangini is much more technically advanced and that he's more "skilled" but that doesn't mean that everyone has to like his drumming. In my honest opinion I was expecting more from him on ADToE. Note that I'm not saying that I think that he did something wrong there or that his drumming wasn't rock solid, cause it really was. What I'm saying is that I think that he was far too anonymous, both in the mix and in terms of what he was actually playing. This could of course be due to him being new and DT writing the album without a drummer present. I'm really hoping that we'll truly get to experience "Mangini unleashed" on DT12, after all the countless hours I've spent watching his clinics and various sessions on the internet I truly feel that there's probably next to nothing that this man can't do on the drums.
If we look beyond the drumming it's only natural to feel as if Portnoy left a big hole in the band when he left. After all, he was more than just "Dream Theater's drummer". Call me crazy but I almost (but just almost) look forward to seeing the behind the scenes material on LALP as much as I'm looking forward to experiencing the actual concert. In my opinion we have yet to see what Mangini truly brings to the table from a social point of view, how his presence affects the group dynamic. And don't even get me started on the possible and hinted at "behind the writing process" kind of thing that Over the Edge seems to have done with them in the studio while creating DT12, I've had a craving for one of those for years now.
Anyhow, yes, I was really sad when Portnoy left and I truly miss him. Yes, I do still think that the band is quite possibly better off with Mangini anyhow and yes, I do enjoy all the other records that Portnoy put out with other musicians nowadays, especially those with the brilliant and multi-talented Neal Morse. They'll be doing the second Flying Colors album as well as the fourth Transatlantic album this year. Sometimes I do feel that Portnoy is becoming something like "Neal Morse's semi-permanent side-kick" though and I wouldn't mind if they formed something more permanent together, a band that they'd be able to call their "home" while still having the possibility to do fun and exciting side-projects such as the occasional Transatlantic album.