I am using Cosmic Shuffle (Hybrid). Its worth for the price (less than 15K). Last 6 months I am suing it. I already gone for long rides ( max 120 KM) in normal roads and Gut roads. But I didn't try any MTB cycles from Cosmic
I didn't face any issue in shifting gear. But you should remember couple of things about gear shifting:
1)Change gear in proper speed. If you are trying to change to 3rd front gear in slow speed it will be difficult.
2) Avoid abnormal combinations like Front 3 and rear 1
3) If any difficulty in changing gear, you should be able to solve by tuning it. You need to take help from proper mechanic
More over you will be comfortable once you used with your cycle