Over the years I have moved through Verisign, GoDaddy, RapidSSL, InstantSSL and a couple of others and have now ended up with StartSSL.
So far had no problems with certs from StartCom's StartSSL. Like many they have an intermediate on the server but no client problems have shown with FF, Chrome or IE. Good fast support too.
The powerful thing with StartCom is they verify the person (and organization) for class2 certs and once the person is approved they can have certs issued for any domains they can validate as under their control. They do individual validation with two forms of photo id and a phone call.
Domains are as commonly done, via the registry email contacts for the required domains.
Organizations need registration documents etc and a call along with the prerequisite individual validation
The one off fee of $50 or so allows an individual unlimited certs on the domains they validate.
This brings the cost down dramatically and makes perfect sense as the main costs are not actually issuing the certs but validating the identity of the certificate recipient and then their right to get domains validated. Different but a good business model for both sides I think.
I also think (regrettably) few site users are concerned by the issuer though some have been confused by the bar on the EVs and wondered where the info was going!