We booked this late in the Ski season in 2014 and were very excited but worried as the price was relatively cheap. We were far from disappointed with this experience. UCPA is a one stop shop for skier's. Room, food, ski hire, lift passes and instruction are all included in the price and each seems to work seamlessly.
The building itself is very basic. Best described as Hostel styled accommodation and poised to cater for large groups. The rooms were clean and the beds were comfortable enough (though after a week of skiing I could've slept on a park bench). We stayed in a 2 person shared room with own bathroom so if you are looking for the larger share groups, I can not comment here. There was some noise in the nights earlier in the week but this did get dealt with fairly quickly.
The food a buffet style with a good range of options. Just remember that it is cheap and a buffet and you will be pleasantly surprised. I did fall into the trap of having 3 hot meals a day though and paid for it in the end!
The staff were good when initially getting ski gear and lift passes. This is a slow process but as you can imagine there are a large amount of people all doing the same thing at the same time. The only issue we had with staff was at the bar where it was obvious that the staff favored serving French speaking customers over English speaking. Not that this offends me much as I do not speak much French but I was standing at the bar alone and the bar staff would serve a French speaking customer when they came to the bar and then walk away. I did complain directly with the staff members and this was never followed up. Again wasn't a major issue but did stop us from using this facility.
Flaine is amazing and the skiing excellent. We had a major dump of snow early in the week so each morning was picturesque with exceptional conditions for skiing. This location is mostly ski in and ski out and the area has many runs to offer beginners to advanced. The instructors hired by UCPA are excellent and even the experienced skier will have something new to learn.
Overall this was a great experience. I would definitely go back to a UCPA as its easy and offers everything in one package. As for the issues with one area of staff, it wouldn't put me off returning.