It won't matter in most cases, what the extension is as far as ranking for a website. Geo and Keyword extensions might have a little impact but since .xyz is generic then it won't matter.
I would never choose a .xyz over one of the big boys, but if it was the only extension available and there was no other options then I might.
One thing to consider when using an extension that is not one of the ones most people are used to is loosing a part of traffic to the .com version of the same domain. Many people still don't know that .xyz is even a real extension. Because it's fairly new and isn't what people are used to.
If you are only going to be having people follow links and search results, then it shouldn't matter. If you are going to be having any word of mouth referring going on then you might consider one of the norm's. As an example, if you had an online site that sold shoes and the name was "GreatShoes.xyz", then you'll loose some potential customers when someone tells someone else about the site. Many people will go and type in "GreatShoes.com", "GreatShoesXYZ.com" or something along those lines.
Those in the domain and related fields will always know the difference (mostly) but to the average Joe, many won't know .xyz is real.
If you are looking to buy any .xyz domains to sell, I would go another route. These don't get good prices unless you happen to have an ultra-premium name or something that someone just has to have. Even then, the prices when compared to the usual extensions is extremely lower.