I posted my Minigeddon variant for E:A about 1 year ago, so felt it was time to review it based on my own games and tourneys other people have reported.
Happy to say the new version is now live @ http://tinyurl.com/minigeddon
(now also with an easy to download and print PDF)
In terms of rules I added some extra bits as a sort of FAQ (no corner deployment, yes you deploy along the short edge, etc). But the most important change is I've now allowed for tweaked formations to make list writing easier. For example, if you look at the normal Steel Legion list most of the Core formations are above 400 pts so can't be used in Minigeddon. So I propose variations of these too expensive formations to make them fit into the Minigeddon restrictions. At the moment I only really looked at the Epic UK lists for these changes, but will eventually get to NetEA lists like Necrons and so on (edit: had a look and found no fms over 400 pts, so no changes). Some formations, though, I couldn't get in no matter how much I tried, e.g. Dominatrix which is very colourful for the Tyranids but at the end of the day not suitable for minigeddon.
(EDIT:Cambridge Skirmish is a 2k event, not Minigeddon)
EDIT 2: Amended rules as per Onyx's advice below