Some humble suggestions:
- Rating of 0 - Listing things by (and with) the total number of downloads recorded, instead of the number of downloads this week - Use input abstraction functions such as get_param($param[string],$type["integer"|"string"|"html"|"float"],$required[boolean]); and post_param([same args]); to make injection prevention much easier and more standard. - (This probably isn't your area, but it's related.) Making Firefox *always* re-download XPIs, instead of retrieving them from the cache (if they have been cached). - Some Ajax would be nice, where appropriate :-D