In my opinion... the only way a E190 can be a serious threat is if the cockpit crew is at the low end of the pay scale. Having said that... I dont think regional carriers are the way to do this. Follow me for a moment... If CHQ/MESA/etc has a fleet of small props, small jets, and E190s then what will all the senior people bid to fly? The E190. Its the top of the payscale and best QOL for that particular company. Now what if a major carrier like DAL had the E190. Who would want to bid for an E190? Nobody except the bottom of the seniority list. This helps keep the labor costs a lot lower for that particular a/c, which in turn creates a better profit margin as opposed to a regional carrier.
Which majors have the 190s now? DAL, USAir, JBlu? Once all the maintenance probs are sorted out with the 190 it might be a competitive platform, we'll see.