I bought the plugin for 2.2 since none of my h.264 AC3 mkv's would play after the update. The same files worked on the OOB 2.1 firmware. Also, I really prefer the Archos Video app since it's performance is far better than anything else I've tried (probably because it's made to take full advantage of their hardware).
It's correct that the "plugin" that you download is only a small file (840B) that unlocks the feature already present on the device. And the unlock file is hardcoded to your serial# so it won't work on another...
• ROM: Pre-rooted Stock Gingerbread (with mods) • OS: Android 2.3.3 (Gingerbread) • UI: HTC Sense
Archos 70 Internet Tablet
• ROM: Archos 2.3.81 • OS: Android 2.2.1 (Froyo) with Market etc • UI: LauncherPro (0.8.6)
Sony Ericsson XPERIA X1i
• ROM: Touch-IT BT 24001 1.2 • OS: Windows Mobile 6.5 Pro (5.2.24001) • UI: HTC Sense (2.5.20113030.0)
FSC Pocket LOOX N560
• ROM: fsc.newplowe.com • OS: Windows Mobile 6.5 Pro (5.2.21501) • UI: WM Default (Titanium)