This product isn't cheap but in my experience it is worth it. Prior to taking this I used to train 3 times a week but it didn't matter how much I ate I couldn't gain weight. I started taking 2 scoops in the morning and another 2 scoops after training in the evening. I gained around 2-3 lb a week and could notice improved muscle mass and strength after a couple of weeks. The weight gain has gone on muscle and not on the belly. I have now gained 14 lbs in total.
There are cheaper products out there but a lot of them put rubbish in their products, I'd rather pay a bit more and know I'm getting something that is good, and Maximuscle are helpful on the phone if you need advice.
The taste could be improved though, I've tasted better protein shakes before, so be prepared to down it in one go! I've only tried strawberry though so the other flavours might taste better.