I make this flight 2 or 3 times each month and it's much more reliable and quicker than the ferry. If you have carry-on bags, you can have as little as an hour layover and be fine. If you're checking bags, plan at least 90 minutes because the cutoff at the ticket counter is 30 minutes for most airlines.

If you can buy your ticket as a code share so all segments are on a single ticket (i.e. Delta to Seaborne) you can check your bags all the way thru to EIS and an hour would be enough time.