I crossed on the taxi boat from Montezuma to Jaco today and had an awesome experience. Within 10 minutes of starting the crossing they slowed the boat for a pod of dolphins and waited while the passengers took photos until the pod moved on. We also saw a couple of giant green sea turtles, 2 rays, and of course, lots of birds.
The staff was super helpful and friendly. I'd recommend these guys for your crossing. For the $40 per person fee, it sure beats the 5 hour bus ride, which costs an additional $10.