From a pax view the aircraft is well designed. 2 by 2 seating and the most comfy coach seat I've ever sat in. I've dead headed from PHL to IAH on the 170 a 3.5 hour ride and felt more comfortable than a 737/757 or airbus I've rode on before. 2 by 2 seating is way better than 3 by 3. The overheads are plenty big but as in any aircraft could always be larger.
My only complaint (in ref to the cabin) is that there is no closet for crew bags. The small closet (coat closet) in the front part of the cabin has a floor restriction on it plus thats where the extra water bottles are. Thus we have to store our roller bags in the overheads. Not that there is anything wrong with it but I feel that that space is for the pax. I'd be alittle pissed if I went to stow my stuff as a paying pax and couldn't because of a cew bag.
The Dash 8 has a large closet in the front on left side. You can easily fit all three crew roller bags in there leaving all the overhead space for the pax. Flying the Dash it used to piss me off when a crew member would toss thier bag into the overhead while there was plenty of room in the closet. Not that I like to kiss pax butts but we kind of need every pax we can get and not piss them off as their bag gets tossed into the bottom/back while a crew bag rides over their head.
As for the cockpit/flying the 170:
As you can see in my profile its the first and only jet I've flown so I can't compare it to anything but the Dash. The biggest/best advantage flying the 170 over the Dash is climb rates and getting over the WX not flying thru it. It just makes the job alot easier when you can top the storms (most of it) and ice ect. rather than having to fly thru it.
I try to hand fly the 170 as much a possible, usually up to the low 20's then turn on the AP. The aircraft flys nice but the control feedback is thru springs so it gives an artifical feel.
It would be nice if they put 2 heading selectors on the AP panel. Ditto what Steve said about the seat above. As far a ergonomics the seat is fine but they forgot to put padding on the seat pan they just covered it with that "seat fur" stuff, no padding. After 2 hours your a$$ is numb. I cant seem to get the external light swiths also. I'm used to the fwd position being on and every time we climb out of 10000ft I've got to look at the light panel and think, it always screws me up. One night the capt and I were discussing this and we came to the conclusion that its good EMB didn't install and safety or critical function switches like landing gear or flaps like they did the external lights or we'd have big problems.