Apple's MobileMe cloud syncing service isn't living up to its advance billing, according to some of Apple's customers.

The gripe comes because data entered on their Macintosh or PC address books and calendars isn't immediately pushed to MobileMe's servers.

"Selecting Automatic in Mac OS X allows your computer to immediately sync and update when there are any changes on the MobileMe servers," read a support note on Apple's Web site. "Those changes come from your iPhone, iPod Touch, the MobileMe Web site, or another computer. Changes made on your computer will be synced to the MobileMe 'cloud' every 15 minutes."

Often described as "Exchange for the rest of us," the service does offer nearly-instant syncing of data between iPhones and MobileMe servers. Changes made to e-mails, the address book, or the calendars are pushed down to desktop computers and iPhones almost instantly, but the lag on the upstream had some users crying foul.

"This is definitely disappointing, and Apple's sales blurb is misleading if not downright wrong," read one forum post on Apple's MobileMe support site. "They clearly state that 'When you make a change on one device, the cloud updates the others. Push happens automatically, instantly and continuously.' Whilst this is true for iPhones, iPod Touch and the new Web apps, it's not true for the Mac desktop applications."

Announced at the WWDC conference last month, MobileMe is a subscription-based wireless data syncing service that's a replacement for the company's .Mac offering.

The service encountered some technical issues last week during its rollout, as multiple users reported problems backing up data and accessing the new Web portal Me.com. But the company said the service is functioning properly now.

MobileMe works with the iPhone's calendar, contacts, and mail applications in addition to working with Mail, iCal, and Address Book on the Macintosh and Outlook on Windows. Users can manage their accounts through Me.com from any Web-connected device.

Customers can also use the service to store and share photos, videos, and other data wirelessly. The service costs $99 per year and offers 20 GB of storage, with additional storage costing extra.