This.
I am a Uni student and have just started to go paperless, as in I do all my notes on evernote, very rarely use paper. I also commute to Uni, which in London, is a bit of a nightmare and can take up to an hour.
I have a late 2013 rMBP that I used to take with me every day, and even though I'm quite a big guy, carrying that extra weight around all day did get me tired. I therefore picked up a used late 2013 11" MBA i5/8GB/256 for £400 with 2 years of applecare remaining. This thing is amazing, has a proper keyboard (I despise the new rMB Keyboard having played with it at the regent st store), very good battery life and is still quite powerful. Granted I still take my rMBP in some days when I'm revising or am doing heavy statistical work, but for most days to take notes, browse the web or annotate lectures, the 11" MBA is perfect and can be bought for some very good prices now!
To answer the OPs question, if you feel you need it then get it. I highly recommend getting a used one, just make sure it's got applecare left on it!