We thoroughly enjoyed our time staying at the cottage.
The location is great for exploring south Iceland (and only 45 mins from Reykjavik) with lovely views out over the lake. The cottage is in a complex of other cottages of all shapes and sizes, with a 5-10 min walk down to the lake. The cottages are well spaced out though so plenty of privacy and we couldn't hear any of the other cottages.
Hrefna and Thor were very quick to reply to any queries we had (usually under 30 mins) and when we had some issues with the sink, Thor was out that day to get it repaired. Even when we were looking for advice of whether it was worth visiting certain places, they were super quick responding with suggestions/ideas!
The kitchen was well kitted out with pots, pans and even a waffle maker (which we made good use of!)
The hot tub was fantastic to sit out in the evening and watch the Northern Lights (which we saw 3 or 4 of the evenings in the week in early September). Being far away from any major town, meant there was very minimal light pollution for watching the stars.
For buying groceries etc, the nearest major town was Selfoss in the south, which was about 25 mins away which was no problem, but worth keeping in mind. The kitchen did have a lot of the basics though including salt, sugar and flour etc.
Only thing we found a little different and is worth keeping in mind is although there are 2 separate bedrooms, they only have interior walls between them going up to the ceiling most of the way. So it means noise does travel between the 2 bedrooms and the main living area (but are tall enough you wouldn't see over them).
As well, as mentioned by other reviewers, the shower is a separate little building round the side of the cottage. Given the weather was pretty good, this was no issue for us though and there is enough space in the shower space to get fully dried and changed if needs be.
And of course, the very important bit for us 2 geeks, the wifi was excellent (usually 30mbit/s down).
Having thoroughly enjoyed our time at the cottage, we both would highly recommend it.