Something I didn't expect with the Xperia Z was to fall in love with it - upon opening it out of the box, I was in love. It looks gorgeous, performs admirably, and does it all without breaking a sweat. Have Sony gone from underdog to a true competitor? Yes, definitely.
It doesn't have the same plastic feel of the Samsung Galaxy devices, which I've come to dislike over time. Samsung have slowly been sliding in build quality (again, in my opinion) over the years, since the release of the Galaxy S II. The plastic feel of the Galaxy S III, Note II and more is getting a bit too much.
Sony have come out with a great device in the Xperia Z, something that is definitely worthy of your money. I would find it hard to believe that anyone could buy the Xperia Z and be disappointed in it, but I think Sony have a little while yet before they have the name that Samsung have in the competitive smart device market.
If they were to sell the Xperia Z for $399 outright and unlocked, and push it heavily in terms of marketing, it could soar. The problem is, Samsung have already got their foot firmly placed into the market, and whoever doesn't buy an iPhone, buys a Galaxy device.
Sony need to change this, and while the Xperia Z is worthy of this, they don't have the same power in the market that Samsung do.
Long story short, should you buy the Xperia Z? Yes, definitely. It's a great phone, and while it's more expensive than the Nexus 4, the Xperia Z has the Full HD display and being waterproof definitely isn't a bad thing. Besides the issues we experienced with viewing angles, there's not much bad to report.