While the App Store is still the 800-pound gorilla of the appiverse, Google Play is gaining ground quickly. According to the official Android blog, in fact, Google Play is celebrating its 25 billionth download, a feat that Apple accomplished six months ago…

In early 2012, it seemed that even though Android had a huge edge in the OS department, it may never be able to equal the volume of iTunes, in either apps or downloads. With 675,000 apps in Google Play, just 25k short of iTunes’ 700,000, Google is nipping at Apple’s heels.

It officially took Google 4 more months than Apple to hit the magical 25B download mark.

In fact, Google Play is celebrating the milestone by offering 25-cent downloads for the next 5 days. From the Android blog:

Every day you’ll be able to choose from a collection of apps from some of the world’s top developers including Gameloft, Electronic Arts, Rovio, runtastic, Full Fat and more. And all for just 25 cents. We’ll also be offering some special collections like 25 movies you must own, 25 banned books, 25 albums that changed the world and our 25 top selling magazines, all at special prices. Visit Google Play a little later today to check them out.

Takeaway: For marketers, this is actually a pretty significant evidence that you must now take Google Play seriously. Honestly, a LOT of us have be dismissive of the whole Android market… come on, you know you have.

According to Gigaom, Google Play’s revenues are lagging behind iTunes to the tune of about 23% per active users. Still, 77% ain’t bad.

If you produce or market digital content on iTunes only, you may be missing a massive and growing segment of the app market… If you’re writing ebooks, podcasting, or creating mobile apps, this is good news.

Basically, it means that Google is finally figuring out how to fully monetize all those Android users. And as you can see from the nearby chart, that’s about 61% of the smartphone market… and a growing share of the tablet market.