I’ll be developing a very strong one word new gTLD domain (Stocks.XYZ) soon as an experiment (I’ll turn it into a megasite with 100+ articles) and for the most part, there aren’t *huge* differences between developing a new gTLD and developing a dot com, a ccTLD or a legacy TLD domain.
There are however a few things you should be aware of.
For example, there will be some issues with certain browsers. In time, I’m 100% sure new gTLDs will be supported by pretty much all browsers and even right now, there are no issues with most of them. However, there will be occasional issues at the beginning and certain visitors might point out that “there’s something wrong with your site” or something along those lines.
Email-related issues are also to be expected. In time, these problems should and most likely will disappear but for the time being, be sure to keep in mind that you might come across email-related problems.
Next, you have to also take the confusion factor into consideration. If you’re mostly going after search engine traffic, it won’t be as much of a big deal as it would be if you were planning something like an offline marketing campaign (TV/radio ads, billboards and so on) but still, the confusion factor will most likely be one of the most important issues you should be aware of, especially during the first couple of years.
These are (not necessarily in this order) three of the most important issues you should keep in mind. Two of them (the browser and email-related problems) will probably be resolved fairly quickly but as far as the confusion factor is concerned, it will take longer.
New gTLD development comes with advantages as well as disadvantages. On the one hand, you can develop very strong one worders such as Stocks.XYZ in my case but on the other hand though, issues such as the ones I mentioned need to be taken into consideration as well.