Does anyone know of the Hotel King (via Sistina) in Rome?
It has come recommended, but at 99 Euros I am a bit skeptical. Any info would be great.

If you check tripadvisor.com you will find a few recent comments from former guests.
It appears that this hotel has gotten mixed reviews. It seems to be in a really good location near the Spanish Steps however.

BiddingForTravel.com has a really negative review or two about the King. I would still go for it at a low rate, though, given its location, particularly if you don't need air conditioning.

no, we will be there mid March, no air conditioning needed, but I have seen good and bad feedback on this property so I am understandably concerned

All I can suggest is since you haven't made any reservation yet, don't do it if you are having doubts about this hotel. What if you arrive to find that all the negative remarks really were accurate? You still have time to check other hotels. There are alot of suggestions here from others who have stayed in the same location. If you want to pay more than 99 euros/night you have even more choices.