Hmm... A bit hypocritical coming from me, but mainly that's because my carrier is the only powerful capship I have.
I have seen many carriers around- I have counted about 7-8, and that's only the number i've seen and heard of. As far as I am aware - only mine, tenacity's and swiss's are on the order roster.
I've also seen that gunboats are particularly popular - and osirises and (especially) recon cruisers are quite rare nowadays. On the infocards - the Osiris and the recon carriers should be quite common ships (common for a capship that is) whereas carriers should be very rare.
In anycase - I found that the only reason I got a carrier was because it was cheap and relatively good. Now that I have my carrier - I find it is very good - but it is VERY easy to hit and is easily destroyed by any poweful ship, and there is not much skill involved to try to use one. Recon cruisers (which I will be getting soon) are quite a good alternative being small, powerful and unique.