Great!
We stayed here for 6 nights at the end of October as we were attending a wedding. The apartment is clean and spacious, all in one room with a separate bathroom. We had no issues at any stage. The guys in reception were friendly and helpful when we needed to print something. We bought food in so only bought drinks in reception, these were reasonably priced.
The location is fantastic. A 30 minute walk to Fira. Although Santorini is famed for the clifftop houses, it's worth spending a morning / afternoon walking around Karterados... for a less tourist, more realistic feel for the island. The local shops and taverns were great and there's a supermarket 10 minutes walk up the hill. We hired a quad for the few days we were there and you can pretty much see the whole island in a couple of part days. Our friends managed to get around really easily by bus, so no need to worry if hiring a vehicle isn't an option. The main road through the island crosses the top of the village by the supermarket.
The only thing I would add about the apartment is, that a few more glasses, a chopping board and a nice bread knife would be a good addition. Other than that, as I say. Great stay, great location.