Though customers are few, Windows Phone 7 hits 25,000 apps

While smartphone consumers are still taking their time to embrace Windows Phone 7, Microsoft (s MSFT) appears to be having more luck with developers. The mobile platform has reportedly crested the 25,000 app mark for Windows Phone Marketplace, according to at least one tracker site.

WindowsPhoneAppList puts the number at 25,076 right now, slightly ahead of another app tracker WP7AppList. That’s up from an official count of 11,500 apps announced in late March. It’s a far cry from Apple’s 425,000 iOS apps (s AAPL) and Android Market’s (s GOOG) 200,000 apps, but it’s a pretty impressive showing for a platform that just launched in November but has struggled to convince users to sign on. Gartner estimated that Windows Phone 7 mustered just 1.6 million in estimated sales to end users in the first quarter.

The new app milestone shows that Microsoft is seeing some results from its efforts to line up developers and make it easy and attractive for them to build apps. Even without a large user base, developers are apparently getting in on the act, perhaps in anticipation of bigger things to come. WP7AppList shows that new apps spiked in late May and early June.

I originally wrote about how Microsoft opened its wallet to get some early marquee apps into Windows Phone Marketplace. I’m not sure if Microsoft is still doing so, which could be a factor. But it seems like that the growing developer momentum is due to a number of factors including rising optimism in the platform.

With Microsoft’s deal with Nokia¬†announced in February, it puts the world’s largest phone maker behind WP7. The first WP7 phone from Nokia will appear later this year, but next year should be when we see a lot of WP7-based hardware from Nokia. That partnership has certainly won over research firms like IDC and Gartner (s ti), which expect WP7 to edge out iOS by 2015 to be the No. 2 challenger to Android.

But those projections are a ways off, and it will take time for the platform to prove itself out. The bump could also be due Microsoft’s work in courting developers. It’s put together some great resources for developers and in April, it released a set of tools for iOS developers to help them port their apps over to Windows Phone 7. Microsoft released similar tools for Android in June.

With an impressive-looking software update in Mango coming this September, it looks like WP7 is closing the gap on the competition. As I noted, it’s a solid update that helps WP7 catch up in many ways to its peers. And Mango is open for developers, as of this week.

Microsoft understands it’s about building ecosystems and that’s why Nokia felt it needed to pair with WP7, to erect a third ecosystem that could challenge iOS and Android. WP7 has gotten off to a slow start with consumer adoption, and Microsoft still needs to sell phones and show there’s money to be made on the WP7 platform.

App submissions won’t continue to grow if no one’s buying the phones. But Microsoft seems to be playing with an eye toward the long view, and that definitely includes making sure it’s got ample developer support to ensure the platform remains attractive to users. Research In Motion (s RIMM) and HP (s HPQ) should take note, because getting developer support is increasingly a key part of the success of a platform.