While I look forward to ME:A and to see how BW will handle things, but I will miss my old friends. No more drunk Tali, or Joker or Wrex (Shepard), but mostly I'll miss Garrus. Garrus Brokarian, G-money, Big Bird, Captain Calibration, yes I'm going to mis my so called token Turian. I know I'm not the only one. But I know everyone has their favorite, and while we are going to make some new ones it's still hard to let those "people" go. So who will you miss most?
It does depend on the new characters they give us - for all we know they could be ten times more interesting than the ones we've had in the past (not that I wouldn't still like and at least miss Tali, Liara, Mordin, Grunt, Wrex etc. etc. a little)
I mean if we don't get an interesting Quarian, I would probably miss Tali (more so than normal), same for the Asari - if we don't get someone interesting I will miss Liara and Samara more and so on and so forth 
Still, as much as I love all these characters (and would love some kind of twist were we get to meet them again...hell, clones might be cool (at least if they'd remember what the originals did) or flashbacks (like say those beacons Liara makes, to ensure that even if they lose, the next cycle will have a better chance at defeating the reapers!)), I think it's time for new characters 
greetings LAX
ps: Yes, I love the Mass Effect companion characters - but I am not attached to them to the point I can't let go 