I have used the Karbonn A15 for a month or so, and here is what I feel about the device:
Pros: Good 4 inch screen with 480*800 resolution. Impressive audio output with a good pair of headphones with N7 and Poweramp players. Good signal reception and excellent in call volume and quality. Cheap price. Supports all essential apps on Google Play Store. 1Ghz processor with 512 MB of RAM. Android 4.0 ICS.
Cons: Lags sometimes. Mildly graphic intensive game runs smoothly but lags sometimes.(Temple Run, Subway Surfers etc.) Camera does not produce sharp Images. Gravity sensor a bit off.
Review: I got Karbonn A15 from HS18. It carried 25% discount at that time so, I got it for Rs 4425. The device looks awesome from the front but ordinary from the back. Its a dual sim device, so two numbers can be used simultaneously. The display is crisp(~240ppi) and there is a light sensor which adjusts the screen brightness as per the ambient lighting conditions. Initially the device worked very smoothly but as I began to install a number of applications the device slowed down a bit. The culprit here is the RAM which the company claims to be 512MB but in reality its around 370MB. A 100 MB less which makes a lot of difference. But nonetheless with an efficient task manager this problem can be minimized to a certain extent. It sports 1Ghz processor which is good for all the basic tasks. It can play games like Temple Run, Subway Surfers, Fruit Ninja etc with ease. Just make sure you kill all the tasks before starting the game. When both the sims are in the phone, it takes considerable amount of time to connect a call. I removed one of the sims and it started working flawlessly without any lag or delay in connecting the call. Camera is just OK for taking some casual photos. The images captured are not sharp but the look quite good on phone display but when transferred to a PC a lot of noise is visible. There is no secondary camera so video calls cannot be made. Other features of phone are: 3G support which works flawlessly. WiFi with WiFi Direct works nicely too. Around 500 MB space is allocated for Apps. 2 GB internal SD card and a Micro SD card slot which supports upto 32 GB. Currently it sells for around Rs 5400 - 5600. If you can spend about 1000 more you can get yourself a much capable device, the Micromax A89 which sells for around Rs 6200 - 6500. It sports 1Ghz Dual Core processor and 512 MB of RAM actual RAM is~470 MB. Overall its a very good device for the price at which it is offered. Just don’t expect too much out of it be aware of its limitations and you’ll be happy with it.