I had a cancelled flight from YYC-YYZ that was supposed to be on an E90. This was May 2010. Otherwise I've had good luck with the Embraers. I'm on them on the YQR-YYZ and vice versa route quite frequently, and have been on them YYC-JFK, SAN-YVR, SAN-YYC, YYC-YEG and YVR-YEG without issue.
I'm not sure if the Embraers are inherently unreliable; too small a sample size.