I have done TOT on both of my last two trips! Once each trip is enough for me (I would much rather be on Rockin Roller Coaster). I would suggest that you at least try it for the experience. The preshow in itself is really awesome. I'm not so sure that you can chicken out at the last minute though. From what I understood, you can chicken out BEFORE getting on the elevator. I'm sure someone else can verify this.
I have not been on this since they changed the sequences, but in the past when I did it, I was not to thrilled with the drops. I felt like my stomach was rising up into my throat. However, it doesn't last all that long. It doesn't give you a "sick" feeling so I would say go for it - see what you think- at least you can say you tried it!