MOR
Having heard you slate the 400 on many occasions, it's strange that after flying it for 2years I've heard little complaints about the noise inside, vibration(??), being cramped(???) or general unpleasantness. Yes, it's had it's moments of tech problems, however most of these are rectified quite quickly with a power-down.
I've positioned on the 146 many times, and find the noxious fumes rather more unpleasant that the noise of the props on short final when they're put to max.
Whatever the reasons for FlyBE initially going for the Q400, they've certainly found their niche and are keeping the company going. Which is probably why they've ordered 20 more.
With the just-announced cancellation of the RJ's, and a decsion not to go for the 737 or A319/20, it looks like you'll be stuck on the 146 for a few years more. That is until they come to the end of a 'serviceable' life, and while FlyBE are still waiting for the C-whatever to be built, you'll find that they'll end up chaging to a one-fleet company.
Enjoy the Dash!