I did *just this this week.
I have a Nexus 4. I have the $30 T-Mobile plan, and had read wonderful things about the Nokia 521. I wondered if it would be a decent phone. I have a child who's going to need a phone soon, and I thought I'd pick up the Nokia and play with it and see if I liked it. My plan was to just give it to my son. However, I honestly think that I'm going to give up the Nexus 4 and just hold on to this for a while.
Like you, I'm not really into a bunch of apps. The Nokia has most of everything I need -- Facebook, Twitter, good messaging and email, and really nice navigation and music apps. It *is* missing a few of the Android apps I used regularly (like coupon apps), but not to the point where I'm feeling pain. Admittedly, I'm only 3 days into this experiment, but -- I like Windows Phone. A lot.
I've never owned an iPhone, so I cannot compare the experience. However, the 521 does an excellent job with basic tasks. Everything runs VERY smoothly. Like REALLY REALLY smoothly. No force closes. No stuttering. No unpleasantness. It's not as fast as the Nexus - but I wasn't expecting it to be. I just wanted to see what WP was like before I spent any real money on it in the future. Based on what I've seen so far, I wouldn't hesitate to buy another WP in the future. I haven't really missed the Nexus this week at all. The screen is much smaller, but the overall feel in my hand is far superior -- believe it or not -- to the Nexus. I'm a woman with average hand size. I was always petrified I'd drop the Nexus and shatter it, even with a case. I'm not worried about this phone at all.
Dip your toes into the WP pool with this phone. I don't think you'll be disappointed.