"www.cacert.org uses an invalid security certificate. The certificate is not trusted because no issuer chain was provided. (Error code: sec_error_unknown_issuer)" (with Firefox)
May want to fix your own site's certificate acceptance before issuing to others.
I tend to agree. Until CACert becomes more mainstream, it is not as useful, except within a community of users who also use it.
The main advantage I'd see with CACert is wildcard certificates (which you dont get at the first level with startssl). Yes you can generate/maintain your own, but maintaining a PKI rapidly becomes a pain.
With CACert certs, it can be as simple as "sudo apt-get install ca-certificates" to get CACert support (for instance, to validate CACerts used in server to server SSL connections).
May want to fix your own site's certificate acceptance before issuing to others.