I'm a big fan of Fog Creek (having worked there for 7 years). But I'm a little stumped on who this is for.
Without any persistence (Mongo, SQL, Redis, something) this is nothing more than a toy. Right now, the forums suggest setting one up via some PAAS, which obviates the whole "it's only one step" thing. Presumably persistence is on its way, as this is just a beta.
Persistence aside, it's still lightweight for an experienced developer. All of the things listed in Joel's "look what you don't have to do list" exist because they are good practice. In fact, 16 years ago Joel wrote about the 12 things that you need to make good software[0], which, coincidentally, includes almost everything on that convenience list.
On the other hand, if you're just learning to code, not having to provision a server or deal with Git isn't really fixing the hard part. Heroku and GitHub are making that easier and easier. HyperDev drops you right into an active NodeJS project without explaining what package.json is, where you define your views, or even what views are.
This leaves it serving a very narrow demographic, which is often the problem with these sorts of tools. Hopefully Fog Creek will be able to make it more broadly appealing before the shine wears off.
[0] http://www.joelonsoftware.com/articles/fog0000000043.html