50 minutes should be fine, provided everything runs on time. It appears that you're on the early GRR-IAH? I've had better luck with shorter ERJ-to-mainline connections with aircraft that remain overnight at the outstation (thus not as dependent on an on-time arrival of the inbound).

Agreed 100% on this, too. With plenty of opportunity for 5-10 minute delays (departure, taxi on arrival, waiting for gate/jetway operator, gate-checks), I've had enough close calls that I usually choose connections > 1 hour.