Our unit arrived yesterday and we installed it today. Installation was not so complicated. My husband was able to follow instructions in the manual and the video that was posted on the site. I have to mention that instructions were slightly different but I guess it was not important and either way could have been followed. An only hiccup we had was with "conversion piece" for the water pipe. We ended up using the one we had before. It fit perfectly and we just moved on. 

One other thing to note, it did not perfectly fit the toilet model. It's ok but not perfect. So I wouldn't say that it perfectly fits any oval toilet. 

So far the unit functions well otherwise and we are happy with the purchase. We did not try this particular brand/model before buying but we tried some other ones before. This model functions just as well as the other one we tried and is twice cheaper.