In my experience, accessing SQL Server via ODBC in Perl is a bit hokey. Not undesireably slow, mind you, but for the sites I've had to use it for, I haven't had an extreme user load.

It bears mentioning that my scripts do not use mod_perl though. I would expect there to be some performance gain there, but some of these scripts were written while I was still a baby Perl programmer, and I have not yet had the time to make them play nicely with mod_perl.

That being said, I like the ODBC interface simply because I can port my scripts to *nix and only have to change my connection parameters in my app's config file. If you anticipate a heavy user load or performance hit, you may wish to consider the ADO route.

Good luck!
MrCromeDome