Apart from following the optimizations mentioned in existing answers (not much helpful, was still painfully slow), doing below did the trick for me.
HP Notebook with 6 GM RAM and i5 processor I have, still android studio was terribly slow. After checking task manager for memory usage, noticed that there is a software called "HP Touchpoint Analytics Client" that was taking more than 1 GB memory. Found that it's a spyware installed by HP in Windows 10 after searching about it in Google.
Uninstalled a bunch of HP software which does nothing and slows down the system. Now, Android studio is considerably fast - Gradle build completes in less than 30 seconds when compared to more than 2 minutes before. Every keystroke would take 5 seconds to respond, now it is real time and performance is comparable with Eclipse.
This might be true for Laptops from other vendors as well like Dell, etc. HP really messed up the user experience with their spyware for Windows 10 users. Uninstall them, it will help Android studio and improves the overall laptop experience as well.
Hope this helps someone. Thanks.