To state my opinion up front; this synth is VERY good. But I'll elaborate on that.
First of all, Guitarbro (the developer) choose to leave any effects like a chorus and a delay out of the design and I think that decision was a very good one. Because of that you get to hear what this synthesizer is really capable of. It's oscillators sound very analog and the filter is among the best I've heard in a software synthesizer. They are so good that Logana sounds quite impressive WITHOUT any effects. There are not that many software instruments that can pull that one off.
However, when you download Logana you'll find a very capable multi-FX unit in the package that can be used on other instruments as well.
The GUI is made by Limeflavour which means it is top notch. It makes Logana very inspiring to work with. It is laid out very logical and makes it a good synth to start with if you want to learn sound construction.
Being mainly a run of the mill VA, Logana does have some very nice features; 3 oscillators where the third can act as a normal oscillator, a sub-oscillator and as a modulation source. It has a highly optimized filter that goes up to 36db slope, which sounds incredible, and a modulation section that let you cross-modulate the oscillators in a number of ways. It's not your modular monster but it has a nice balance between complexity and usability.
All this makes Logana a very useful instrument, I would almost say for 'bread and butter' sounds. It can do screaming leads and nice bases but also very fat pads and synstrings. Throw in the FX-unit and it can easily match many other good synths including some commercial ones. For myself; let's just say I don't need a Little Phatty anymore (yes, I think it is THAT good).
There is no manual or other documentation, and as Logana is quite new, it will take some time before the tutorials start to pop up on Youtube. However, Guitarbro is active on the forum here on KVR, and besides being a nice guy he's very active in listening to the users and updating Logana accordingly. Several small bugs have already been ironed out in the current version and the patch-memory, originally holding 16 presets has been changed to 128 slots.
Logana currently comes with just a few presets but they show off the great sounding oscillators and filter. More presets will come as several users (including myself) are working on patch-banks for Logana.
If you like VA's then definitely give Logana a try. It's one of the best (FREE) ones in it's class.