Do a search at Sound on Sound for reaktor and there are 2 good articles on it. http://www.sospubs.co.uk/

I don't find it that hard to use using the ensembles created by others. I just use it as a vst instrument in cubase and it works just fine but I always need to record it as audio as it tends to eat up alot of cpu power. Some really good emulations of vintage synths. And the sounds are amazing to say the least for a soft synth!