It could be a bit rougher for a good

The edges are a little more square than the rounded edges of the 520/521, which make it a bit easier to hold.

He hasn't had any problems with this one and enjoys it quite a bit.

A bit disappointed.

The photos are good on the phone but when printed a bit blurry (low pixels)

Still getting used to all these features, getting my sliding and tapping right takes a bit of doing, but THIS PHONE IS A STEAL OF A DEAL AND WORKS GREAT, camera is good enough for me, sound is clear, screen is a bit hard to see in bright sunlight, good otherwise, battery life is ok to good

This is fine if all you are doing is getting directions, but if you are listening to a podcast, the interruptions can be a bit much

Great phone for price, a bit slower on performance side, if you are accustomed to Iphone or newer galaxy

It has a slightly larger 4.5" screen that is also a bit brighter - both nice upgrades - and it adds 4G LTE support for faster data connections.

but I have always believed that it is a bit underpowered

Great phone for price, a bit slower on performance side, if you are accustomed to Iphone or newer galaxy

However, it was a bit tricky initially to get the WI-FI Calling switched on.

Second, the replaceable shell/case is a bit too smooth, making it a little slippery

This one actually kinda exceeded my expectations a bit

The 521 occasionally would lag a bit while resuming an app, but the 635 with a quad core CPU and a 20% MHz bump hardly ever shows me the app resumption screen, and even when it does it's only for a second or less

This last bit surprised the heck out of me --- basically, this now obviates the $70 Vivofit

Still getting used to all these features, getting my sliding and tapping right takes a bit of doing, but THIS PHONE IS A STEAL OF A DEAL AND WORKS GREAT, camera is good enough for me, sound is clear, screen is a bit hard to see in bright sunlight, good otherwise, battery life is ok to good

A little research makes me thing it will be a bit tricky

My cell phone is inherently prone to irreparable damage... slips out of my hand as I fumble for my car keys... slips off the bathroom sink and into my toilet

It has all the features I liked about the 521 and the same handy T-Mobile/Nokia built-in apps (Cortana, T-mobile wifi calling, Here Maps/Drive with offline GPS) but is noticeably faster, has a more attractive design and larger screen, and has LTE capability