OP doesn't need UA in MCO but for general interest, I use it all the time. I just take the shuttle to the UA pier and then return when the lounge closes at 8 in good time for the 8:55 flight that is always delayed.
The train is literally 5 minutes each leg, and both are on the same side of security so very little hassle. Depending on which train track the trains are on, sometimes you can even exit one train and dash in the exit doors of the other before they close. Worst case, you walk 20 steps around the end and into the departure area for the shuttle.