[cd34]

I would say 30% of virtual hosts support it as it is the only way to allow legacy php4 versus php5 parsing on the same site. Of those, some will prevent environment changes effectively denying clients the ability to run fastcgi processes. Virtual providers tend to dislike it because it creates extra processes running on the machine. Dedicated machines generally have it, but, usually not configured.

We're finding more people using mod_wsgi which is a very similar technology and I believe Catalyst works under it. It isn't as widely deployed as mod_passenger. CGI still has the stigma that CGI is bad -- a carryover from the mid '90s.

If you're asking the question I think you're asking, developing an application that depends on it will probably run into deployment problems putting you into a situation of running a hosted solution, or having a very small list of hosting companies able to use it.