We couldn't have been happier with our stay here. The owner speaks good English and made us very welcome - in fact we had problems with our online payments leaving him 20 Euros out of pocket. We agreed to pay him in cash when we arrived, but when we offered it, he declined it. Although a studio flat it isn't pokey and was perfectly adequate for 2, although would have been a little more crowded with 3, but doable. It's in very easy reach of the Carrefour so if you want to cook at the apartment you can, although keep in mind there is a microwave, two hob rings and no oven. We were inventive and had some awesome meals but for less confident cooks, this might be an issue. It's situated close to the Rock and if you're an F1 fan, the pitlanes. It is more or less the opposite end of Monaco from the casino, but actually, I'd recommend that option. It's quieter and more real - locals still live in this area. The restaurants nearby are really no more expensive than any city in France (although all the prices go up and the quality goes down over the F1 weekend).
In conclusion, I'd say that as a lawyer, I was a bit anxious about booking an apartment where there was no contract and I was just making electronic payments to someone's bank account overseas. Part of me did think we might get there and find we had nowhere to stay but I could not have been more wrong - so if you have these kind of fears - this is definitely a place you can trust.