Ok. It does track the phrases but I agree that the stats are not currently built into the plugin in an easy to use form. I think the best way forward might be to use the data from SearchLogger and provide the statistics in ExtraStats. SearchLogger is actually one of the few plugins which does provide historical data - you just need to know how to display it. I'll need to find out how to check whether a plugin is installed first.
I see what you mean about the snapshot. Collecting the data on a daily/monthly basis is quite memory intensive which is probably why people have stayed away from it. I will have a go at seeing what else I can add into the ExtraStats plugin.
Maybe I'll try to get the category breakdown in ExtraStats first as - having not really investigated it at all - I think it should be straightforward I may be sorry for saying that when I'm still working on it in six months time!
When you say top 5 categories what do you mean by 'top'? Do you mean the categories with the most visited links? And would you want the bars to show the total number of link hits in that category? If you want the category pageviews then this will be in the SiteStats plugin.