WhatsApp annoys the hell out of me. Almost everyone I know uses it, but it doesn't work on a computer, which is the only platform I'm willing to use. I ended up installing BlueStacks, but it's a bit buggy, very memory hoggish, and I have to leave it open to receive messages on WhatsApp.
I wish everyone would just use something that's cross-platform compatible, like Skype. Oh well, maybe if Facebook acquires WhatsApp it'll become natively usable on PC, even if it's only browser based. I'd much rather have it in a browser than inside an Android emulator.