I'm always surprised despite this iPhone struggling with some more heavy apps and being very low on RAM, just how snappy it is with most actions on a daily basis, it is quite a similar case with the iPod Touch 5th generation, where if you disable transparency on iOS 7+, it really sorta shines there. It still looks very nice for a phone from 2011, and has ton of apps compatible even with being left out got iOS 10.
Although I am an Android guy in this field, I don't mind the fact that this thing is decent for basic usage nowadays and some heavy games perform well, knowing optimization for specific devices is basically a requirement from Apple.
16GB nowadays on more modern phones ain't enough but on a phone like this, it might be sufficient without the need for an SD card, but nowadays, I don't recommend it unless you are brave enough to dive late into older devices in 2016+.
I just got one of these for $40 this year off eBay. I must say that it is a lovely device, especially for the price! Awesome build, Sense is OK (compared to TouchWiz), and a decent camera besides the pink tint issue. One of the main highlights of this device are the speakers, and boy are they great. So much better than any phone I've ever used in my life (besides the M8 and M9). This device still performs like a champ, whatever I throw at it. I've used Android Marshmallow on here, and even that works great. But now I'm back at Sense 5, Android 4.4.2. Sense 5 feels more responsive than 6, 7, or 8 (yes, I've used partial Sense 8 on here) so I use it. I'd say that this device is better than any of the "budget" devices out there today for it's display, speakers, camera, and software.
My first Android device besides my Kindle Fire (ah, good times). The stock experience was a good one, no doubt. Despite only being 5MP, the camera wasn't bad at all. The display wasn't disappointing, either. I had a lot of fun with custom ROMs on here, and all of them ran with ease on this hardware. Although 8GB internal storage wasn't great, there was SDcard expansion so no big deal there. The soft touch back and the Moto dimple are just great :)
I love Windows Phone and Windows 10 Mobile, and I loved this phone. It was such a steal -- just $30 on eBay. Although the ecosystem was lacking, smooth and well designed software made up for it. Everything I needed was there for the most part. Although this phone wasn't the most premium looking or feeling (well... look at the price), the removable battery, expandable storage, and switchable backs are something I still miss on my phone today. Lumia 520 will always be a favorite of mine.