But I can't talk only about cloud sync, even if it is the hottest thing on the planet today.
There is another battle, which is very interesting to watch. The battle of the App Stores. Here, we have Apple App Store vs. Google Android Marketplace vs. Microsoft SkyMarket (or whatever they will call it eventually; looking at how they changed SkyBox to My Phone, I am betting for MarketStore...). There are more competitors here, like Palm App Catalog and BlackBerry Application Storefront. One per operating system, Symbian coming soon, JavaME DNF but you never know...
The latest news on the app stores front are juicy. First, Apple has passed the 20,000 apps mark. The news comes from Apptism, an iPhone app activity aggregator. The number sounds about right, since Apple has announced they passed 15,000 on January 16th. However, if 5,000 apps a month are added, the accelaration is shocking.

Google is trying. The Wall Street Journal reported that the Android Marketplace will start accepting paying apps this week. Keeping up with Apple is tough. Making money is a good reason to publish an app, however stupid. If Google does not allow a developer to make money, it will always be a second choice for many.
The advantage of Apple, though, is big. They have your credit card.
I repeat: they have your credit card.
You might think they don't, but if you look into your iTunes you will find it. They collected it once when you bought that 99c song for your daughter. Or when you walked into the store and bought an iPod (did you notice they ask you for your email when you pay? Boom, credit card linked...).
You cannot download a FREE app on iTunes, if your credit card is not valid. It happened to me, my credit card was expired, I tried to download Funambol on my iPhone and I could not make it. I had to go back to my PC, put in the new expiration date on my card and voila', the free Funambol app installed on my phone (billed for zero dollars).
Having the billing element set up, with the credit card ready for you to pay is BIG. Google does not have it, people will have to go through an additional step to buy. Bye bye impulsive buy :-))
That said, I am sure Google will soon have all your credit card as well. And your location with Latitude, as Apple already does (if you have an iPhone). What is Microsoft going to do to match evil?
We'll see, the app store novel has yet to be fully written. It is going to be fun to read.