I had the Lumia 630 Single SIM handset for about a year. Based on my experience, Ill list out its advantages and disadvantages:
Adavantages:
Strong build quality.
Gorilla Glass and ClearBlack screen at an affordable price.
Decent camera for daylight photography.
High storage capacity, with 8 GB internal storage and support for microSD cards of upto 128 GB.
Good battery life, as Windows Phone does not hog resources like Android.
Excellent after-sales service.
Disadvantages:
Expensive for the money. When it launched, the phone was priced around Rs. 10000/-, yet it has features inferior to the competing devices. It has only 512 MB of RAM, and even though WP works well on a 512 MB device unlike Android, there are phones cheaper than the L630 that have 1 GB RAM. It also does not have a front cam and a flash, and the screen brightness cannot be adjusted automatically based on the outside brightness.
No accessories are provided like earphones and USB cable. They have to be bought externally. Only 2 brands of earphones work with the L630: Nokia Coloud Pop and Panasonic earphones, both of which are very expensive. It is so bad on the part of Microsoft to sell a phone with inferior features for a high price and yet not provide basic accessories along with the phone.
Call quality is not too good and I have experienced many call drops.
Underwhelming performance, with slight lag, especially if more than 3 apps are running in the background, and the irritating "Resuming" screen which occurs if an app running in the background is opened.
As far as gaming is concerned, the phone should be strictly used only for basic gaming, as only basic games like Temple Run, Subway Surfers and Candy Crush etc. run well on it.
Mediocre audio and video quality.
My verdict:
The Lumia 630 is a strictly OK WP device which is a very good option for users who want to experience the Windows Phone OS for the first time and swear by the Nokia brand, but cannot afford the more high-end and superior Lumia handsets. For users who merely use their phones for calling, social-networking and basic gaming, the L630 is a good option. On the other hand, it has lesser features than its competitors and is let down by a mediocre performance. If you wish to buy this phone, my sincere suggestion is to avoid it and check out some of the WP handsets marketed by the Indian companies, which provide awesome specifications for a low price. But if you really want a Lumia, then look at the better and cheaper offerings which are now provided by Microsoft like the L532, L535, L540 and the L640.