Unlike the S4 (mini) I find the matte plastic back the Lumia very high quality, it is secure and does not creak. The touch screen responds well, with the top of the screen to detect a slight "black mist" is (deliberately?).
Windows 8.1 is running very smooth, which is hard to beat in this price range from other operating systems (despite 512MB of RAM). The battery life I would rate as average (1.5 days at medium screen brightness and normal use + Appanwendungen).
Previously, I had not a smartphone, but I could get used to the fast Bedinung. I find that very appealing Benutzerinface and varied than the competition; compared to previous Windows Phone versions are planned for this latest more opportunities for user customization available.
Apps like WhatsApp, Facebook, etc. run course without hesitation, but some apps in the Windows Store is well known (yet) present (Spotify, most recently!). Who can take this light deductions in purchase will be well served with the Lumia 630.
POSTSCRIPT: After nearly 1.5 months Use:
Unfortunately, the phone hangs between simple on / crashes - with completely normal applications such as starting the Facebook app, the full-screen playback of videos or playing music via Spotify.
On the subject of Spotify: Unlike advertising promised in Spotifys, the mobile music listening for WP user is not free; there is a premium account required (unlike Andriod or iOS). In addition to frequent Abstüzen the app, the Premium features associated with this mobile is hardly worthwhile because Offline playlists can not be saved on the SD card, but only on the relatively small internal memory of the phone. In general, it seems currently 3rd party (Apps) is not to be possible on Windows 8.1 on SD card access - pity.
This of course has nothing to do with the Lumia, but I wanted to mention it yet, if Spotify is a selling point for a smartphone.