We did the Lynx from TTC to Sea World and then grabbed a taxi there to USO (much closer so it was a lot cheaper!). For the 4 of us it cost 18 bucks on the taxi and 6 bucks total on the bus tickets, so $24 to get us to USO.
My parents would arrive today and rent a car at the airport and meet us there, so for us it was a one-way trip (another reason why mears wasn't the best option for us)
But even if it was a round trip it would still have been cheaper than mears.
The TTC-Sea World bus doesn't have lots of stops (basicly at DTD and one more before SW if I'm not mistaken) so it didn't take too long.
I completely agree that continuing to Central station and getting another bus there would take forever! That would surely be one crazy thing to do as you would ride a lot more than you should, going to downtown orlando and then returning.