Our family have stayed twice at the Mont Helmos (both during August) and would happily stay there again. Situated up in the mountains in the town of Kleitoria, within walking distance is the town square with several tavernas and coffee bars, with the usual bakeries/banks/chemist etc just off of it. We were lucky enough to be there when they had the town festival with a parade and traditional Greek dancing all night that is highly recommended.
It's a good location for exploring the region - the picturesque town of Planitero and Kastria cave lakes are a short drive away, while slightly further away is Kalavryta (for skiing during the season) and towns like Vytina (that has lots of small shops selling local products such as cheese) with little villages in between.
As people have mentioned, the pool is great...the only slight possible drawback to this is that it and the pool bar can get very busy with locals. The hotel itself is fine, perhaps a little dated in parts (eg the showers are temperamental and the rooms have old CRT TVs but hopefully you aren't going to waste your time there watching TV!), but nothing major that would put you off staying. The breakfast buffet has a good selection and the smell of the pastries baking in the morning makes it well worth waking up for!
Finally the owner and staff were great and couldn't be more helpful. Oh and they have a couple of friendly dogs too...