Because I play a lot of correspondence chess and these days what with engines being employed by almost all players, opening preparation is more important than ever, so I investigated using Chess Opening Wizard. It appears that it's actually geared more towards OTB players who want to improve on their opening play.
Chess Openings Wizard (desiger Mike Leahy) is similar to the 'tree' function in ChessBase, but more advanced. You produce database called ebooks. It's generally recommended for players rated about 1800 up to expert (2000).
Studying openings for players in this range is not the waste of time it is for lower rated players because they already have an understanding of the basics. For most non-masters, no matter how well they know an opening, they tend to collapse as soon as they are out of their book simply because they have such a poor understanding of basic middlegame and endgame concepts.
COW is useful for opening preparation which it does in the form off trees. The advantage to this tree method is that transpositions are accounted for so you don't have to ferret out the same position that can be reached through different move orders.
You can also purchase a number of ebooks, but like all opening books, they will be out of date. It's better to make your own ebook and then copy and paste the games into a PGN file and then import the files into your own ebook.
There are three versions: free, express and professional. You can download the free version; it is a trial version of the express version. This is rather strange, but the express version becomes the free version after the trial ends and it can be used permanently.
The trial of the express version comes with a number of ebooks which can be viewed even after the trial expires. With the free version you can view ebooks, but changes can't be saved. That makes the free version pretty much useless. About all you can do with the free version is find transpositions and use the training feature to run through all the variations. A lot of the stuff covered is pretty obvious.
One major complaint about downloading the software from official site is that you get a ton of Spam from the owner...at least that's the rumor.
Free Version: Comes with demo ebooks that describe all the openings by name and ECO code. To get the free version (and apparently a lot of Spam) you sign up for a 30 day trial of the Express version and after the 30 day trial is over it becomes the free version; it will work indefinitely.
Express Version: You pay $67 for it. Has the ability to edit your own openings and do analysis with an engine.
Professional Version: Costs $167.
For a comparison chart of the feature offered see HERE
I decided that Chess Opening Wizard it not a product in which I have any interest. You can't do much with the free version except look at outdated opening analysis and the Express version is not worth the price because if you are a beginner, low rated or average player, you shouldn't be spending a ton of time on detailed opening study anyway. And when it comes to playing correspondence chess, I don't need to memorize anything plus I can make my own opening books using any number of programs. Maybe the Pro Version is worth $167 if you're going to be playing your FM, IM and GM peers.