I claim here that MobileMe is useless and only good for people with minimum email requirment not every minute users and I tell you why:
To make the story short, Mobileme doesnt have incoming filtering system if you only intend to use Mobileme with Iphone. I could add 18 folders to Mobileme's web account and all 18 folders appeared in my iphone but all mail was delivered to inbox since this feature is not available.
So back to my original comment, its good if you receive few emails a day but not many emails from dirrent companies. I get somany emails in my inbox that I miss the important ones and have to go through all emails to find the one im after. This filtering system is available on any free webmail service but Apple is too busy counting $$$ earned from Mobileme to fix this.
I agree that MobileMe webmail is very limited and does not have the ability to create folders and filters to manage messages on the MobileMe site. But you have to look at MobileMe as what the services is about. It's about Sync data
FROM your local Mac (mail, calendar, photos and files) as the starting point, then to MobileMe (Cloud) to iPhone or other Macs. For this to work perfectly, (1) your Mac has to be on and running/connected to the internet at all times...this is very important for what YOU want. (2) your MobileMe account is active on the iPhone and Push turned on. If all you have is a MacBook/Pro and is with you all the time on the road then the mail thing is not going to work properly (I'll get to it in a minute). I would suggest to get a cheap Mac Mini or something that can run Mail and stay connected at all times.
Here's the setup.
1. You have GMail or whichever email service/server auto-forward to MobileMe because you want the Push function. I suppose you have outgoing emails (SMTP) configured to GMail's so your recipients don't get confused by the sender.
2. On your Mac, setup MobileMe mail account in Mail...from the menu File > Add Account... and add your MobileMe account info. Set Outgoing Mail Server (SMTP) to Gmail (or the SMTP server of whichever account you have forwarded to MobileMe). To set this go to Mail > Preferences > Accounts > select your account > Under Account Information > Outgoing Mail Server (SMTP) > check "Use only this server" and select the drop down menu and chose Edit Server List. Add
smtp.gmail.com under Server Name and click on Advanced. Use default ports and SSL, enter password authentication, your username and password.
3.
Creating Folders and Rules
This is where you set up your folders like you've done in GMail. From your Mac, in Mail, create a New Mailbox (click + at bottom left of Mail and select New Mailbox). Select your MobileMe account as the Location and give the mailbox a name ie. Finance, Marketing, Operations, John Doe, etc. and repeat until you have all your proper folder you want your mail to automatically go into. These mailboxes will appear on the left pane in Mail under your MobileMe email address. This gets sync'd to your iPhone or any other Macs you have running Mail configured to your MobileMe account. The mailboxes will appear as how you've set them up. This is what MobileMe does well.
Next you set up your Rules. Go to Mail > Preferences > Rules. Click on Add Rule. Give description for your rule ie. Finance, Marketing, etc... create your conditions and move the messages to the related mailbox created above. Create new rules for each mailbox. That's all.
4. Set Mail to check for new mail Every minute (Mail > Preferences > General > Check for new mail). That's all for Mail.
5. Last, configure MobileMe, go to Systems Preferences > MobileMe > Sync > Synchronize with MobileMe
Automatically and check Mail Accounts and Mail Rules, Signatures and Smart Mailboxes.
This is what I have set up and it works perfectly. All the mail stays on the Gmail server and the Mail app on the Mac, iPhone and MobileMe are sync'd the way I have them set up locally. The rules / filtering works perfect for me and pushes them properly on my iPhone. The same with my Calendar. All are sync'd instantaneously as advertised. For me the service has been great since Apple got it all working and I don't find the service useless as you say. Good luck with it!