The ROMs include both the GDR2 update from Microsoft, which adds the FM radio to the phone along with the Data Sense app. The latter keeps track of your data usage, telling you which apps are using most of your monthly allowance, and also reminds you how many days are left in your billing cycle.
The Amber update, for Nokia phones only, includes the Smart Camera app which offers the Action Shot mode. This allows you to snap an action sequence and have it come out on one photograph. Amber also brings the always-on clock and the double tap-to-wake feature among others.
You can find the ROMs for the Nokia Lumia 820 and Nokia Lumia 920 below, along with instructions on how to install them. Again, if you're not sure what you are doing, your best bet is to wait for the official release.
source: WindowsMania.pl (Lumia 920) ), (Lumia 820), NokiaViews via Engadget