After hearing it was better than the Maag, I had to try it.
I don't know if it's better than the Maag as I've never tried that plugin, but it does exactly what I needed it to do.
It boosts the part of the top end that you actually want boosted, without any artifacts, harshness or nasally resonance.
It treats top end with respect.
The keepgain switch is brilliant as you are then making EQ decisions made firmly on frequency rather than on volume and the trap of thin king something is better because it sounds louder.
I have EQs for low end, general EQs for everything else, but this is now my go-to for detail and clarity in the top end. Great find !.

The curves match up exactly to the endorsed Maag EQ4 at Plugin Alliance, just the numbers on the dials are a little different. This one also gets a tiny bit more air boost at max setting.

Luftikus is superior because of double-click-to-reset knobs; and the gain compensation, which this EQ seriously needs, it's pretty insane without it. Also appreciate the mastering mode, this should be in all plugins.

Well, the plugin works very solidly in my Windows 7 and Windows 10 systems with Studio One Pro 4 and 4.5. I am so happy with it that I sold my maag eq4 plugin. While there are minimal sonic differences between the two, I find the Luftikus better sounding and more pleasant overall.

Some people claim that you cannot have enough EQs, while others say that one fully parametric EQ is usually all you need. I belonged to the later group for some time, because let's face it, there is not much you cannot do with those modern highly flexible EQ monster plugins. But this one has several arguments that speak for it:

1. It has a nice, big GUI that is clear and legible and features friendly colors that say "Come on, use me, turn my knobs, it's fun and I don't bite!".
2. It is limited to four bands, one shelving and one boost filter. No myriads of options, Q factors, M/S en/decoding or analyzers. Simple and easy.
3. It has a "mastering" mode which emulates stepped knobs on a hardware device. Doesn't do much for the sound itself, but helps make fast decisions in my experience.
4. "Keep gain" is a neat function that prevents your ear from believing something sounds better just because it is a tad louder.
5. Sound. Well, there's an old but ongoing discussion about digital EQs and sound quality. Fact seems to be that programming digital EQs is not exactly rocket science and the sound of an EQ is mostly determined by its curves. Personally, I haven't found a modern EQ plugin that destroyed my sound, if at all, it is my fault for making the wrong decisions. So yes, I'll say this plugin sounds good...
6. Cool name. "Luftikus" was the name of an old sailing boat my father once owned. Totally not important, but now you know it :-).
7. And last but not least, it is free, it is even GPL which is still relatively uncommon in the plugin world. So you can download the source code and extend it, if you like (an can).

So what can one use it for? Well, the limitation to six bands and the broad Q clearly states that this is is a classic sweetening EQ for use on selected channels or on the stereo bus. Personally, I like it very much on the bus, just a slight dip on the 160 or 640 Hz can help remove some muddiness, add to that maybe a small increase at 20kHz and you're done.

Are there any cons? Well, considering you pay nothing, not really. The "analog" button's effect is kind of homeopathic in my opinion, I didn't really hear any difference. According to the dev, it adds a slight overall noise floor and a tiny difference between the left and right channel. Use it or leave it, it won't make your mix better or worse.

Personally I would have liked another band at around eight to nine-ish kHz for having the option to removing a bit of sharpness in that area, but then the next guy wants another band at 473 Hz and you have to stop somewhere.

All in all a very welcome addition to the freeware EQ world. Thumbs up.