I've breastfed 2 children and have never owned or even used a breastfeeding pillow. So no I don't think it's a necessity, but a lot of people do find them useful. 

OH bought me a (v cheap) v shaped pillow and I used that with a normal pillow.  After a while, couldn't be bothered faffing around so normal pillows did the trick. Shoved them down the side of the sofa when anyone came to visit!

Unlike others I found that just propping up with normal pillows always ended up in problems (whilst out and about etc fed without a pillow of course, no problem, but not day in day out).  I had SPD in pregnancy and have problematic neck and back anyway. 

I tried a few (at groups and clinics) and found this one BRILLIANT and all the others not that different from an assortment of normal pillows

http://www.boots.com/en/Boots-Inflatable-Breast-Feeding-Pillow_25410/

It's only £10 so not pricey, and is inflatable (def wouldn't recommend inflating and deflating regularly - it's a faff) so if you don't use it or have finished with it and want to put it away for next baby it takes up very little room.

I found it far more solid and supportive than the soft BF pillows which I found useless.

I will be trying to find my old one (lent it to various mates and lost track of it!) but otherwise will buy a new one  ready for baby 2 due in 10 weeks.

 x