The R22 is so popular due to one reason: Cost... cost of purchase, and perhaps more importantly, cost of ownership and maintenance.
The R22 will bite your arse in a heartbeat if you're not paying attention, but from what I can see (based on a heckuva lot of research on the type) that a properly trained pilot can fly them without fear of being Thusly Smited.
FWIW, I have been "analyzing" the personal helicopter alternatives closely over the last couple years, and I think that, given my economic situation, the R22 would be what I'd end up buying... Most of my 100-plus hours is in the S300C/CB, and I have the SFAR73 signoffs for the R22/44... With my "vast" experience (yeah right), the R44 would be what I'd really like to own, but I prolly won't be able to fork over that US$300K anytime soon - so my options are limited to the 2 and 3 seat ships... I have seen that the S300 series can exhibit some pretty eye-opening non-scheduled maintenance at times - whereas the R22 seems to be much less prone to this sort of thing. Thus, even though I'm not a huge fan of some aspects of the R22 (size, cargo capacity, the cyclic arrangement), it seems to end up the winner from an economic standpoint.
The other ship that I still need more data on is the Enstrom - I haven't flown one yet but hope to do so soon... A local operator has an F280C that I want to take up.
cheers,
Dave Blevins