I did keto for a few months a year ago. The first couple of days are hellish as you go through keto flu, but once you get into the swing of it and figure out what you can and can't eat, it's alright.
I can't say there were any huge changes to my health or anything like that, but I was doing it in combination with a slight calorie restriction, so I guess there's that to factor in. Two big changes I can remember are that my acne cleared up a lot, and my taste palette changed a lot (while I was still on keto) so that I was finding dark chocolate surprisingly sweet. I think it had to do with reducing the amount of artificial sugars in my diet generally. I stopped after a couple of months though - I missed fruit way too much, and I was doing very strict keto so I had literally no leeway.