Ok to all the guys who are confused about push services or want to know why its not working..
First of all, push service is for only iphone/ipod touch and web apps. Not for macs/PCs. For macs/PCs its the same syncing service that was available in .Mac system preferences.
I think you may be in error here. As it says on the MobileMe page (http://www.apple.com/mobileme/features/) under "Push email. Push contacts. Push calendar.", which has been quoted earlier in this thread:
MobileMe stores all your email, contacts, and calendars in the cloud and pushes them down to your iPhone, iPod touch, Mac, and PC. When you make a change on one device, the cloud updates the others. Push happens automatically, instantly, and continuously. You don’t have to wait for it or remember to do anything — such as docking your iPhone and syncing manually — to stay up to date.
Also, check out the accompanying video about it in that section.
Clearly, Push just isn't pushing correctly (yet), albeit rather sporadically for some, to or from Macs and PC's.
Seems to me that they're probably more worried that the iPhone pushes correctly at the moment. I'm sure they'll get to the Mac/PC push once they've got everything stable. But it clearly says that Push will work with Macs and PCs.
I'd consider it a little shady if all they're really doing on the Mac/PC side is automatic syncing, yet selling it like that in the description above. Time will tell.