Currently with apache/mod_ssl, if DHE is enabled then a 1024-bit ephemeral key will be used. I found the following quote in Adam Langley's blog:
Ideally the DH group would match or exceed the RSA key size but 1024-bit DHE is arguably better than straight 2048-bit RSA so you can get away with that if you want to.
So it appears that he is advocating something like
DHE-RSA-AES256-SHA with 1024-bit ephemeral DH keys over
AES256-SHA with a 2048-bit RSA key. My understanding is that 1024-bit DH (ephemeral or not) is of comparable security to 1024-bit RSA. Why would he make such a recommendation? Does he value the forward secrecy offered by DHE that much?