We (mid 20s couple) stayed at Mediterranean Royal for 10 days in June 2011.
This hotel works together with Mediterranean Beach, which is about 100m further towards the sea.
This meant that we could eat breakfast at 'our' part of the two hotels, but for lunch and dinner we had to go to the Beach Palace.
We didn't mind. 'Our' part has it's own pool with bar, which was usually quieter than the bigger pool at the 'main' complex.

I will point out positive, negative and neutral points.
Neutral being things that didn't bother us (much), but might be worth mentioning for others.

POSITIVE:
- Both hotels are beautiful and very clean, which we think is essential.
- Staff were very friendly and available 24/7, they helped us out efficiently and with a smile whenever needed. I heard staff speak fluent english, french and german.
- We had no problem getting any regular beds by the pool or at the beach. Keep in mind we were here in mid season. Especially the smaller pool at the 'Royal' part was always very quiet and relax.
- Our room and terrace were very spacious. I do believe we took a slightly upgraded room however. It was only 50€ extra in total, so probably worth it.

NEUTRAL:
- The hotel is right next to the airport. This was a big annoyance to others at the hotel. Besides some sort of practice by F16 jets one day, which were a LOT louder, the regular planes didn't bother us at all though. Flights aren't -that- frequent and they don't fly at night, as far as we heard.
- At the 'Beach' part, where you eat lunch and dinner, there are indeed quite some cats as i had read in a review beforehand. We personally love cats, and they weren't a hindrance to us. If you hate cats, they might bother you, but they didn't beg or jump on tables or anything like that, so we couldn't see any problem with them passing by.
- Maybe irrelevant to this review, but I wanted to include it; the supervisor (staff referred to him as 'the boss') is a real pig. I saw him harassing the female workers very suggestively on a few occasions, clearly to the dismay of said females. I found this to be extremely inappropriate.
- Though food wasn't necessarily bad, choice wasn't very elaborate and it was the same thing everyday. Leftovers were clearly re-used in a 'new' dish the next day. We ate out several times and considered the food to fit in with the price we paid for the hotel, but some people were outraged by the food. We found them to be exaggerating quite a bit, but if brilliant food is an absolute requirement for you, granted, this might not be the all-in for you.
- The bed was rather hard. I like it that way and slept like a baby. It comes down to personal preference I think. the first night there was only one very thin pillow for each of us, but we quickly received more pillows after asking for it.
- The TV was very small and very old. We couldn't care less as we don't even touch TV when on holiday. I'm not even sure if it worked as we didn't even test it.

NEGATIVE
- Drinks included in the all-inclusive package are the standard syrupy softdrinks, 'local' beer and wines, all from those 'hoses' typical for all-in hotels. No surprises there, but besides that, they serve only 'ouzo lemon' and I believe it was rum-cola. That's it. We were a bit let-down by the lack of any cocktails.
Drinks are only free until 10pm as well. And they do respect this very strictly. Once I was waving at the bar for one last drink at 09:55pm, only to be ignored for 6 minutes to then hear 'it is 10:01 PM, the all-inclusive has finished'.. It's wasn't the bartender's fault, but the above-mentioned 'boss' was clearly keeping him from serving us during those 6 minutes, because he already decided for himself it was time to close.
Even this little incident aside, we found 10pm to be rather early to close down.
I don't believe we 'profited' from the all-inlcusive, and with what we consumed, it would've probably been cheaper to take a hotel with breakfast or half board.

CONCLUSION:
Beautiful hotel with great staff (minus Mr Pig, but you normally never deal with him directly). We felt we got our money's worth, though the all-in package was a bit of a let-down.
We enjoyed the absolute beauty, cleanliness and friendliness of the hotel above-all, and had a great holiday.

TP:
Between the 'royal' and the 'beach' part, is a small mini-market called 'LOUIS MARKET'. This is one of the cheapest shops we found on the entire island, AND: you can use his terrace and use FREE wifi.


PS: Santorini is absolutely amazing! And we've been to quite a few great places to compare it with!