This hotel is actually called YANNIS not Yiannis, and yes its definately the same place, even the rep always wrote Yiannis and ALL the Olympus stuff has the "I" too.
After reading this site, I had my doubts, but there was no need. The hotel is great for self caterers, yes the kitchen is definately a cupboard, an actual wooden cupboard, I thought it would at least be a built in cupboard. I had to take a picture. But if you opt for B+B I advise you to take a kettle at least (for pot noodles or coffee).
The only BAD point was the breakfast on B+B is awful, bread and cheese, with some juice! Don't bother, go for the full English, no faults there.
The pool is lovely, from 0.8m to 3m deep, nice to dive into to cool off. Plenty of sunbeds, friendly atmosphere.
They must have changed the rep that people mention here, because our rep was polite, helpful and happy, and we saw her every day except for 1.
Also the cleaning has improved from what people say. We arrived at 5am Saturday morning and it wasn't cleaned till Monday, but then it was cleaned EVERY day during the week.
THe views from the rooms are stunning. If you want a fancy room, don't go here, but if you want somewhere to change and sleep then definately do!
I didn't think much of the menu options at the hotel, and found a MUCH better selection and cheaper options at a place just down the hill called Calypso, lots of vege dishes too (gf was vege). If you want to continue drinking into the night, B52's was a very friendly place with plenty of atmosphere.
Oh yeh, the hill, not as abd as everyone makes out, can be knackering, but thats as much to do with the heat than the hill.
I have photos if you want them.

We stayed at Yannis in Ipsos, we was the last pick up so the journey was nice and short, I saw many tired/sick looking faces of people who had travelled much further!
We went in the last week of May, there was NO queues, we just got on any ride we wanted to.
Only bad point, the enclosed tube rides that "do not" use the rubber rings are lethal on your back and you feel like you're being put through torture! Only do the ones with rings!
They have 1, 2 and three man rubbers rings available.
The wave pool was a bit disappointing, sitting around for ages and ages for 5minutes of waves!
The trip is from 10am-4pm, which gives good time for rides, food and drying off period! Lockers only cost 3euro, (actually 5euro but you get 2euro back when you hand key in).

Best place for a decent meal before the evening. Nice selection, nice surroundings, nice staff, nice meals!
Only bad point, the mixed grill was a let down, I think it was the most expensive thing on the menu, but not their best dish!
GF really liked the Fajitas, and the chicken dishes are well worth the money!