This is a thoroughy fun piece of software. All those cheesy organ sounds from groups that couldn't afford a B3 are now within your reach. However, be sure that you are looking for that transistor organ sound, because this isn't anything like a B3. If you think the "strings" button will give you anything like a Solina strings, you are also wrong.
Let's put this a bit more positively. This is a very idiosyncratic instrument, and it's very good at what it does: reproducing that very retro sound, warts and all. It is also unique: there is nothing else like it.
There is a long list of presets, so that should get you under way to exploring the various possibilities of this organ.
I have a few complaints about the interface. Due to the way the light falls on the switches they are actually dim when on and bright when off. Also the layout is initially a little confusing, but I won't take you more than a minute to figure it out.
In the value-for-money category, you'll have to decide how much you're going to use this kind of sound. Personally, I find the price slightly high for a plug that I may use once in a very long while. But that's different for everyone. If you're screaming for this sound, then it's quite cheap.
On Mac OS X this plug works fine through the AU-VST adapter, but I hope DashSignature will make a native AU version anyway.