They have an online demo which you may want to try and see the features before you buy it. In the past week or so, I have played with the SQL Server version of this ad server and my opinions are as follows. The first thing I look for in any software is the set of features it provides AND the features that can be tagged on to the existing features. The program provides a stepped approach to advertising - Advertisers, Banners, Campaigns, Zones. Campaigns are one or more banners of an advertiser and this makes it very flexible to have one banner participate in multiple campaigns.
Zones represent slots or even themes.
For example, the whole site can be one zone or only the bottom banners could be one zone. This is highly useful if you have a large site with different set of prices for slots or even multiple sites. Reporting is another tool that makes an ad server a worthwhile buy. If you are not looking to provide your advertisers with reports, you are better off using the ad rotator component . The program provides four sets of campaign reports - by banner, by day, by banner by day and by clicks.