It's amazing to me how many of the "reviews" on MacUpdate and VersionTracker are by people who obviously haven't given the software a full testing. To compare Sticky Notes with Apple's free Stickies is wrong... Sticky Notes adds a number of huge features that make it a definite buy!
First, you can attach any sticky note to an application. I use this feature constantly... This way, the stickies I need when that application is running show up when that app does. You can arrange the sticky notes in a very subtle manner so they don't draw too much attention to themselves, too.
Second, the stickies are incredibly easy to arrange. They're like little magnets and will line up however you want.
Third, you can use Rendezvous to send sticky notes to other people on your local network. This is huge, and we use it all the time in my house.
Fourth, you can add hyperlinks to web URL's as well as to folders and documents on your hard drive. This means you can set up a sticky note with a link to that deeply nested folder that you sometimes use with this one application, and you don't have to add it to the Finder or other places. Very cool.
Finally, you can add graphics and other media files to sticky notes, and you can invoke a little formatting palette to do some basic text formatting.
All in all, this is simply a much better version of the Stickies idea, and well worth a try!