Is it worth upgrading from iPad Air to iPad Air 2?

Do you take a  lot of pictures/video with your iPad? Then think about it.
Otherwise, unless you get a really good price for your previous iPad, it probably doesn't make sense to upgrade, since the improvements are nice (better screen technology, much better camera, faster processor) but the iPad Air was also very good already.
I went from an iPad 4 to the Air 2 and the increase in speed was very noticeable.  However, you may not see as much of a difference between the Air and the Air 2.   There would be two reasons to upgrade, in my mind:

1.  Touch ID.   It is nice being able to protect my iPad with a complex password and use my thumb to unlock it.
2.  Support for 802.11ac WiFi, which will give you better performance streaming video locally and will help future proof you when higher speed Internet connections are available.
Well , if you really really want a better camera along with a8x super powerful processor, an Ultraslim 6.1 mm body ..... You should buy it. Otherwise for normal/ moderate uses, it may not be so urgent. I'm a man , who is still happy with iPad with retina display(4th gen).
My iPad2 just died. It is now a cold, dead slab.
So, yes, I will be ordering a new iPad Air 2 first thing tomorrow.
I bought it for Touch ID.
What are some hacks that PhD students should know?

I am currently a PhD candidate in Aerospace Engineering. My research work pertains to developing simulation techniques for modelling and simulating composites materials.Few of things which I believe are useful for a PhD candidate:Documentation: Most of my research activity involves coding. Since most of the physics I simulate involves complex equations, it is always a good habit to comment

Is being a school teacher worth it?

Yes. As a retired NYC teacher after 35 years, I can say unequivocally that it was worth it. Sometimes the laws were rigid and wrong-hearted; sometimes I didn't have the right (or enough) tools, and sometimes it was too hot in the room

Does anyone in India own a high end Tesla vehicle like the Tesla Roadster?

I am sure that some dude in Delhi or Gurgaon must be owing one.. North people cannot survive without importing one. Tesla can be charged with a normal plug point with a particular voltage. Not necessary to have charging stations. People in India do have surplus money to buy fancy vehicles, specially Sainik Farm area of Delhi. So I