Jumping in late on the on-site bandwagon here, but it also depends on what kind of vacationer you are.
If you are the planning type that likes to get to the parks early, plan all your rides and thrive on sticking to a schedule and commando touring, FOTL may not be as important.
We are not that type.
We like to sleep in, have a leisurely breakfast in the club lounge and then head over to the parks when the rest of the crowds start pouring in.
Having FOTL allows us all this and still be able to be glared at by the same people waiting for their first ride on MIB as we pass them yet again for our 3rd or 4th ride in a row. Didn't like our score? Missed that one alien? Just go ahead and get in the express lane again. It is not going to take us 20-60 minutes to reride, or on a slow day, even 5 minutes.
We like to walk around the parks and decide on the spur of the moment if we want to ride something or not. We hate sticking to a plan. If we want to ride Spiderman, FOTL gives us the freedom of not having to worry about what the wait lines are going to look like.
We can eat when we are hungry, rather than trying to fit it in our touring plan. FOTL allows you to make snap decisions without having to factor in wait times.
Lastly, we do put value on our hotel stays. The prices are more than fair for the type of resort, 4*, you are getting. And if you do your homework, you can usually find a decent discount on top of that. It may not be at the time of booking, but if you keep checking, you usually can find one. There is only one stay we have had where our initial booking price stayed the same and we couldn't find anything lower and that was over a holiday weekend.
So, it all boils down to what kind of vacation you want and what value it has to you.