I bought this phone as a spare when my current phone had broken. I have to admit that I was a little skeptical about buying this phone, i really did not think it would manage all i needed to do, however when i received it i was pleasantly surprised!
The 635 is a perfect size; slim and lightweight with great graphics and a vivid color display which is better than the iPhone (in my opinion) in direct sunlight. I like the fact that I can individualize the home screen and have an up to date basic view of all applications (email, calendar and social media etc) without having to open each of them individually. The camera produces good quality pictures and has some nice options for shooting in different modes/scenes.
Battery life is very good for a smart phone. It can survive a full day of pretty heavy usage and charges fairly quickly too.
My only gripe (and I'm picking to be constructive) is that it isn't as repsonsive as some up to date phones. Some of the applications take a second longer to load and there is no front camera, which in all reality, I never use anyway!
Also another down point is that the windows store does not have as many apps as say android or apple so you are a little limited there. You may have to use third party apps instead of official ones.
That being said i think its a great little phone for a good price!
Overall, excellent value for money.