I bought lumia 540 few months ago. Basically im a windows lover so im not worried about the os, in my point of view windows is always better than android, ofcourse android consist of several apps and more functions but for a decent use windows is more helping because it give more battery life, makes the phone smooth and hang free, easy documentations etc .
Talking about my experience with lumia 540, the phone is good to handle and looks good, it gives good battery life, and smooth usage, internet browsing was great and good . It gives amazing selfies it occupied with wide angle 5mp cam which is awesome, main 8 mp cam is also great. One of the attraction I found is low SAR value I think windows 8.1 is very good and user friendly and I liked the platform very well . I strongly recommend to who looking for a better phone under 10000