Mostly good, with some bad. Anytime an RJ replaces a turboprop, that's a good thing for the passenger. The turboprop is a substandard product. Passengers have told airlines such resoundingly both in surveys, and with their dollars. Comair and Continental Express are cleaning up with regional jets, as is Atlantic Coast.
However, RJ's are sometimes used to replace full-sized narrowbodies, which may be undesirable to the markets affected. For instance, Delta pulled 722s this summer from Grand Rapids and Dayton and replaced them with RJ's. The 722s, according to Delta's press releases, went to "more lucrative transcontinental routes." GRR and DAY got more frequency with Comair and ASA RJs, so if frequency is your criterion they didn't do badly.
Full-size narrowbodies generally are more comfortable than any regional aircraft, including the RJ's which at least offer jet speed and quiet to their passengers. But I'll take an RJ over ANY turboprop, any day, where available.
Need a new airline paint scheme? Better call Saul! (Bass that is)