Just a quick update... I don't know if you can properly register an Archos 5IT on Google Play... I already registered mine on Google Market... but it seems Play works just fine on the A5IT, right alongside Market.
The trick is, you just access it from the browser, not from a dedicated App.
I just updated Trillian (a chat client I have installed) using "Play."
One thing that's better with "Google Play" is that it will tell you, unambiguously, which apps are compatible with your device. Of course, it would seem that MOST applications on there aren't compatible with the A5IT (due to the version of Android, mainly, but also in some cases due to features which aren't present... such as, for example, the need for "multi-touch" control).
This is something that might've prevented me from spending a few dollars on a couple of items which are incompatible with my Archos. On "Play," they definitely say "not compatible with your device." And yes, they're not compatible. (Example: "Plants versus Zombies")