The OnePlus 3 is not waterproof, like many of the other smartphones on the market, but that is what you will sacrifice when you are paying a little less. The OnePlus 3 is a major upgrade for anyone holding an entry level phone right now and for just $399, you are not going to think twice about it.
If you are already thinking about picking up the OnePlus 3 in black, keep in mind that it will come in another color at some point. According to at least one online source, the OnePlus 3 is going to hit the market in gold as well. In most cases, there are tons of options online if you want to change the color of your smartphone with a custom case.
All in all, the OnePlus 3 is a solid smartphone and if you are looking to upgrade from an entry level phone, look it up to see if it is available for your area.