I started in an old Prijon Taifun and then bough a Rainbow Reaction (because a guy from our club could get a good deal from Rainbow). The Reaction was a big banana, and I found it terrible to cross eddy lines in it.
When the RPM came out, I immediately bought one and loved it. It was so much easier to paddle and it could front surf on auto-pilot, so I had loads of fun in it.
However, soon after that, planing hulls became more popular, and my next boats were a Riot Hammer and a Wavesport X. I loved the way they behave on waves, but also when running whitewater I found those boats so much more predictable than any of my previous boats. Since those days, I have always put beginners in modern boats as well, even though many guys in my club said that one should start in a displacement hulled boat (probably because that's what they were used to themselves).
I would indeed not let people start in an RPM these days, and if I'd paddle one myself, it would be for nostalgic reasons only...