"The Lumia 520 looks good, it's got a decent screen, it rarely stutters or slows down, it's great for calls and messaging and might it just be the best entry level Windows Phone handset you can buy." - TechRadar
XPD^ / DemiseNZ
Disclaimer - It wasn't me, the dog ate my keyboard, my account was hacked, I was drunk, ALIENS.
xpd: I recently purchased a 520, love it - camera is great for what it is, except no flash.
On the OS/app side of things, apps are a little lacking compared to iOS/Android, but most of the mainstream things are there. Windows Phone 8.1 is due out soon which adds a few more functions and needed changes :)
For the price, I'd give it a 4.5 out of 5.