Dash cruises at just under 360kt TAS, which is a bit slower than the 146-200 used to be, but not that much, while burning around 1000kg an hour - you can see why the bean counters love it. Putting it onto off-peak longer routes in the winter makes sense if you know you aren't going to fill a 195. Granted it isnt as spacious as the 195, but give me a Dash seat over a middle seat 3-3 layout on a 146/RJ anyday. The time difference on a domestic sector between a Q400 and a jet is usually between 5 and 15 mins longer depending on sector length - if the price is right and the dep times suit their schedule, most pax wont care what they fly on.