I've been on Rita nad nemesis and rita is still one of my most feared rides (just coz of the acceleration) but I love the feeling on nemesis, as I'm sure you will!
We took stephen(Gould's younger bro) age 13 on nemesis not long back for the first time and he was really aprehensive, having never been on a major coaster before (apart from spinball whizzer the same day which he hated)
and when we got him on nemesis, me and gould sat him in the middle and we both held on to him for support but he cried all the way up the chain lift.
we were really worried we'd done the wrong thing. it was the scared-ness and nerves that made his first ride on nemesis not as good as it could have been, but still as soon as we got off he said 'can we go again?' [:)] and we ended up riding it loads that day. the only thing i think he perhaps found was that he should have gone on air first (at alton towers) as his first major ride, as he found it calmer and more relaxing than nemesis. but yes. def ride it, you'll enjoy it