This is a non issue. Windows phone is becoming more and more ram efficient and were getting windows phone 10 as well
It most assuredly is an issue! If you want to play most games in the store the lack of a full GB if RAM will impact you negatively.
And merely stating Win 10 will fix everything simply underscores how obsolete the 635 will be as Win 10 is at least 10 mos away!
I've owned the 635 from release and the build materials are cheap (crappy screen, plasticky back) but the build quality is high. This phone can survive a drop or two most definitely.
Unlike the 830s there are no touch issues. All the buttons are responsive as well as the screen.
It's the crappy and incomplete OS that is the problem.
Just as the Denim update brings features only to the newer phones you can expect the 635 to receive squat from Win 10.