CdTrix mentioned that the AXE would be a good comparison and I agree. I will go with that since I've already owned both and that seems to be what people want to compare it to.
I owned an Axe for quite a while, since I was an early adopter. Then, due to finances, I sold it along with a bunch of other things and then once things stabilized again, I bought the Etha.
I have not gotten a chance to play a full day yet, but I've put about 1500 rounds through it, just testing things out and running around. It is a VERY solid option in the 4 - 500 dollar price range. I won't be one of the people to say its better than the Axe, its just different.
The Etha has a lot going for it. It shoots smooth, what most define as 'kick' is actually just vibration. I felt the Etha was easier to control than the Axe when shooting. Mostly because the Etha is very well balanced when you put a tank on it. It is louder than the Axe, but quite a few marker are . It is not like the thing is setting off car alarms in the distance or anything, I would even say its quiet, but not as quiet as the Axe.
As far as quality goes, this feels really, really, solid. I can tell the tolerances are strict when building it, and the whole GRN (Glass re-enforced nylon) panic is unfounded. The material feels VERY solid and not like plastic. At least not to me. I personally love the case which is solid and tough. I remember being somewhat bummed out that the Axe did not come with one.
As far as ergonomics go, I like the Etha more. While the Axe is a stellar shooter, I always had a little difficulty getting a decent grip on it. Truth be told the Axe is a longer gun, and I think I just prefer smaller guns. The trigger is another thing that is a big deal for a lot of folks. I love the trigger on this thing, light and quick and easy to adjust. To be a bit more descriptive, the trigger seems to be very thin, making it easy to walk. I may be wrong, but I believe the trigger is the same one on the ETEK. There is a bit of side to side wiggle, but when you shoot you simply do not notice. All in all, the Etha wins on simplicity (Ive already taken the whole thing apart). Very easy to maintain, very easy to setup, and very easy to program (even with one light). Unfortunately you may not find an army of people that have gotten to play a full day with one just yet. I hope this helps.
I owned a g4 and now and Etha. I will say that I liked the trigger on the g4 more than any gun I've has, but the Etha out shoots the g4 in terms of smoothness and noise. The Etha is also abut more comfortable.
One thing to consider for the g4 is the techt bolt. Change the gun into a new marker from what some people say.
I have owned an axe and sold it (needed money BAD). I was just going to buy another axe when my finances picked up but then saw the Etha. Since I am a bit of a gun whore I decided to get it instead. No regrets. I will give you the run down
Noise: axe is quieter, but not by much. I was surprised by that cause I just assumed the Etha would be loud.
Kick: when I think of kick I think of barrel rise, and I know I will get some heat for this bit I felt the Etha had less barrel rise than my axe. What the Etha does have more of is vibration. When I shot the axe it was like clicking a mouse, the Etha you do feel vibration.
Ergonomics: strictly opinion. Determining which has better ergonomics is like determining the best color, opinion. I for one like the feel of the Etha more, but the axe did feel damn nice.
Barrel: I have to put this in because I think it is significant, the shaft 4 barrel on the Etha is awesome. It is nice to see a quality stock barrel in a lower priced marker.
Quality: both guns are well made, period
Feedneck: I don't think any of the axe owners will disagree with me on this one, the Etha feedneck is better. A feedneck, however, is a heap upgrade.
All in all I think the Etha is going to be a fierce competitor to the axe. We will be seeing a lot of both on the field.
I have to say that the talk about Etha kick is overstated. I shoot axe and just got an Etha, there is little to no barrel rise on the Etha. What you do feel is vibration, but the thing shoots real nice.