It’s very bad mobile because it have hybrid SIM slot and not have clear sound Anti Blast Screen Protector - so, even if your display breaks because of some power related issues - your display will not blast like samsung phones. This sounds funny but I think vivo have simply did a good job by adding this feature.
b) Funtouch OS 3.0 - this is latest from Vivo and it definitely improves the overall experience of the phone.
c) smart screen shots - you do not need to press buttons to take screen shots of Vivo Y66. Just swipe your fingers and you will be able to capture screen shots
d) screen recording - want to share what is happening on your screen? use screen recording function. you will be able to record and share with anyone over whatsapp or even you can mail them just like a normal video clip.
e) eye protection mode - Vivo Y66 have got eye protection mode - which reduces strain while we use mobile phone in night or in dark conditions. most of us use mobile phones while sleeping. I think this is very very nice feature.
f) call recorder - though it is not auto call recorder and it is manual but it is very useful. now to record calls, we do not require to add any app. the recording quality is also good.
hope you will find my above tips for Vivo Y66 useful.