phpAdsNew, and the forked-off "max media manager" now apparently going under 'openads', are decent, heavyweight systems. the plugin just helps to get the system included, but you still need to install (and understand) the bulk of phpAdsNew. You can easily do it without the plugin if you have a basic grasp of PHP.
It's a good system if you are a medium-to-heavy site, running real banner systems, selling spots, etc. I ran it on a lightweight site, as it gave me an idea of what was being shown -- but I had to nuke it when the really, really old version I was running ended up with an exploited spammer vulnerability. If I needed the power, I'd go back to it in a heartbeat (not keeping it up to date was my fault, though I never got any update messages in the administration UI as I'd have expected).
The reality is that for some people it'll be overkill. But for others, you'll have a hard time finding all the features you want in any 'small script' ad manager.