My boat is an older (1989) Skeeter with a 150 Johnson on it and takes a little time to get on plane. Folks with hydrofoils installed what differences have you seen? Worth it?

Poor fix for a bad set up. Call Steve or Josh they can point you in the right directions, there are better option out there than a fin.

http://www.stevescustomprops.com/

http://www.hydrodynamics-usa.com/

As fordnut pointed out, you would be better served by getting your boat/motor/prop setup properly to try and resolve the issue. That being said, I have an 86 fish&ski with a Johnson GT150 on it and was experiencing the same issue. I used to pull skiers and tubers and it would take a while to get up on plane. I added a hydrofoil and it resolved the problem. I continue to use it on the same boat to this day (30 years and still going strong). I did lose a few MPH of top-end speed but can still run ~62 which is fast enough for me. I love the fact that the boat pops up on plane in just a few feet and I can cruise at under 15 MPH and still remain on plane.