Is anyone experienced with doing a hosted exchange server setup?

We have some customers who have exchange servers in their offices currently, but are looking to get rid of the noisy server running in their closet and have someone host it for them. So, I think this might be a whole new product line for us. Just looking for some comparisons to provide to the customer for hosted vs. non-hosted exchange server setups.

Cartika Hosting, they are doing it.

http://www.cartikahosting.com/Hosted-Microsoft-Exchange-Hosting/Exchange-Hosting/

That is what we're looking for ... Are there any sites with recommendations on what to do or not to do when starting exchange server hosting?!

That is what we're looking for ... Are there any sites with recommendations on what to do or not to do when starting exchange server hosting?!
It will be complicated and you'll want to build up your Exchange expertise in-house. See:

http://www.msexchange.org/tutorials/Hardening-Exchange-Server-2003-Environment-Part1.html
http://www.msexchange.org/tutorials/Hardening-Exchange-Server-2003-Environment-Part2.html
http://www.msexchange.org/tutorials/Hardening-Exchange-Server-2003-Environment-Part3.html
http://www.msexchange.org/tutorials/Hardening-Exchange-Server-2003-Environment-Part4.html

In general you should probably live in msexchange.org and msexchangeteam.com and have people spend some serious time researching how other hosting providers do it.

And of course you have to be signed up for SPLA. There may be other requirements to be an "official" Exchange host but I'm not sure what those are. I'd poke around Microsoft's site some.

http://msexchangeteam.com seems to be having some problem, maybe some temporary one.

The only requirements to offer hosted exchange is to be an SPLA provider, but you do need alot of experties and knowledge to work with exchange, it can be an odd beast at times and it takes a long time to get to know the ins and outs and to be able to diagnose the problems that can, and probabley will occur.