I live near a Ferry stop, I've never done the regular commute, but ride often, as I prefer it and walking vs the subway. It can be pretty nice.

To help you factor times, the time tables on the ferry's website are accurate, they are spot on with times and basically won't go faster or slower than those.

You'd always want to be at the ferry spot 8-10 minutes before your scheduled departure time. Then on the other side, M-F there's a free shuttle bus that will take you around midtown. Unless you're immedietly on both sides, this city basically has a way of making every commute around 45 minutes. Could be subway, could be ferry, could be bike, usually around 45 mins. lol.

Would I do it regularly? Yeah totally, it's a super chill ride. You can bring your bike on now without an extra fee. The ferry is the best way to travel IMO. And you can use your commuter dollars towards it. If you think you do get motion, it's not too bad, but just keep a handful of ginger candies in your bag in case you want them. And they sell beer and coffee on board too.