Two of my businesses use the iCal publishing.
Actually, MobileMe's terms of service prohibit its use in a business environment, if I am not mistaken.
Given the relative instability of the service and frequent downtime, I think it's a good idea to keep it that way.
On that note, I think it would be great if Apple introduced another tier of service for businesses. MobileBiz or something, maybe MobilePro. That could include more advanced web features to make it easy to create functional business websites (shopping carts, credit card processor integration, contact/order forms, etc.), the ability to make e-mail addresses for your employees (say 10, and then an extra add-on fee for each one above that), and finally included online collaboration (kind of like Office Live).
Finally, Apple could do a better job of hosting it to make sure its more reliable and faster than the consumer-grade MobileMe.
Of course it would be geared toward small to mid size businesses, such as individual consultancies or small (less than 10 or 15 man) operations.
Wow that would be sweet. I'd pay $249 a year for that!
Also, I agree with the other guys here. Paying $99/$149 for MobileMe may not be worth it to all, especially if all you do is use e-mail, but it IS worth $50-$75 for the individual account and $100 or so for the FamilyPack if you get it on eBay or another place and use synching, the iDisk, and some of the other features.