When we changed from Bell 47's to R22's for integrated courses at a commercial school, we found the time to solo wasn't any different at about 12 hours. Indeed the time for readiness for solo was actually slightly less due to the excellent lever/throttle correllation, and even more so when governors were fitted.The 12 hours was an artificial minimum set to reflect more time given to EOL's.
References to R22's being twitchy and unforgiving is not helpful to students to whom confidence is paramount. R22's are unforgiving of poor instruction by instructors who lack confidence themselves and revert to the "do not do this or that, it is dangerous" method.
The basic principal should be that all techniques within the flight envelope and permitted by the flight manual (including EOL's) should be taught and the student should be happy that he/she can handle the unusual without continuous dire warnings about death and destruction which is hardly conducive to a calm and confident approach
R22's also require a disciplined approach to checks and procedures, particularly with reference to carb heat. As our students transitioned directly to S61's and Super Pumas without problems, it must have something going for it as an instructional tool.