The E170/190 series has been very reliable since mid 2006 from my experience. The first two years yielded a lot of bugs, any many of those were a result of excessively tight software tolerances (too narrow of a window of time for the multiple computers to report back and agree). Flight Control No Dispatch was the big whammy, but spurious versions of that message are really just something to look back fondly on.

I can't speak for the other E-jet operators, but at Republic there may be a few reasons that the OP may have noticed poor reliability. One is lack of familiarity with the type. There has been a fair amount of inter-certificate movement lately, and a good number of 145 and CRJ guys from CHQ are just coming onto the E170 now. The E-jet needs the pilots to do things in order, or else it can freak out. Older airplanes are generally more forgiving, and allow pilots to develop "techniques" for things like start up. The E-jet doesn't take kindly to pilots inventing their own flows or techniques. I have observed many pilots unknowingly create a list of EICAS messages early on in their 170 experience.

Another contributing factor may be the 190 and its relative youth in terms of software development. The E190 basically started with the original E170 software, and E190 operators have had to go through many of the early teething problems the 170 had. The 170 is further along in software revisions than the 190. Also, the 190 introduced a few new software features that needed some reworking.

One final reason you may see more return to gates on the 170 these days at RAH is you have more unhappy pilots who are less willing to troubleshoot a minor problem over the phone with maintenance while off the gate. i am not advocating using a personal cell phone for company business, but I am saying that over time, you learn what EICAS messages are real no brainers, and can be solved with a 2 minute phone call to MX rather than taking a 45 minute delay or worse. It is all preference, but more pilots are fed up with management and really don't feel like helping anyone out by making that quick phone call.

The plane has treated me well, and the MX cancellations have been less than one per year for me. That seems to be the rule, rather than the exception.