I love the idea of a vanity because it means an opportunity to indulge in my love of vintage furniture. My friend from the States has the most beautiful retro vanity and I love it! It also adds a bit of glamour to your daily routine.
I like the look of these, but they don't quite compare to my aforementioned friend's vanity:
Image source: http://everythingfab.tumblr.com/post/170880804
Image source: http://thatvintageshop.com.au
Image source: http://www.pbteen.com/products/hampton-vanity-tower-and-super-set/
I have a large bedroom, which could definitely fit a vanity, but I'm hesitant to buy one because I'm a renter. Such is the life of the renter: you never know if your next bedroom will have a built-in wardrobe or what size the room will be. If I weren't in the midst of getting my professional qualification, I'd probably get rid of my study table and replace it with a vanity.
One option would be to get a small table and attach a lovely vintage mirror that I already have, to the wall above the table - a modest, makeshift vanity that would suit the unpredictability of renting.
But there are relatively smaller vanities available too:
Image source: http://www.ikea.com/au/en/catalog/products/30158273/
I shall keep my eyes out at second-hand furniture stores and on Gumtree.