If you want seven billion people using it, it's going to be quite necessary to create a consumer-facing canonical front-end.
I'm sure you can get lots of volunteer hackers to contribute if you throw up an MVP on github.
Instead, there's room for Valve's SteamOS, Google's Android, Google's ChromeOS, Canonical's Ubuntu and many more, both commercial and community focused, competing in some ways, collaborating in others.
This announcement is one company that did exactly that, and provided a consumer-facing product built on OSM, who just got bought by a bigger producer of consumer-facing products who intend to do the same on an even bigger scale.
libpcap has tcpdump. linux has ubuntu. http has nginx (and previously, apache).
It would be great if there were a canonical frontend stack for OSM that we could all hack on to make as usable as Google Maps. It should be hosted somewhere central but also ship with easy chef or puppet configs to deploy a stack yourself easily.
I'd get tons of use out of something like that, and I'd contribute to the code, too.
Monolithic engines are great for getting 80% of what your exact requirements are, then you're stuck with a bulky system that you're probably only using 10% of, and it doesn't do the other 10% of what you need.
Something like leaflet.js is nice because it gives you a simple way to present layers on a device, and it's modular meaning you can plug in extra behaviors or develop your own easily.
If a similar approach were taken for the other problem areas, like route finding, traffic monitoring, etc, I'd much prefer that over a bulky platform I'd never want to use the entirety of for any one project.
Of course once these modular components mature enough, no doubt soon, they will be packaged into some service that with a few simple clicks of a button generates the right combination to suit your requirement.
tl;dr OSM should do the data collation and serving and be good at that. Other services should spring up to do their magic with that data. And yet other services should provide easy ways to thread it altogether for a whole world of possible use-cases. (all IMHO of course...)
And this article is the equivalent of say, Canonical taking Debian and saying they're going to make an easy to use desktop linux from it. It will almost certainly be more "polished" and end-user focused than openstreetmap.org, because they serve two different types of users.
Interestingly Wikipedia are actually a user facing front-end for OpenStreetmap data, in fact they have at least 4 projects using slightly different tech to put different front-ends on OSM as appropriate for their usage, e.g. the official Android app uses MapQuest OSM tiles to show articles that relate to your physical surroundings:
https://play.google.com/store/apps/details?id=org.wikipedia&...
and the german wikipedia has a couple of gadgets in the top right hand corner to show the geographical context of the articles:
http://de.wikipedia.org/wiki/Kongo_%28Fluss%29
They also extract a lot of vector data from OSM to hand built appropriate maps and diagrams for articles:
http://commons.wikimedia.org/wiki/File:Aruba_travel_map.png
Again, not always what I'd call polished, but they're making creative use of map data, rather than putting some pins on Google Maps (or on an OSM based clone) and that's a good thing.
This is quite belittling to the thousands of hours professionals have put into the OSM tools, infrastructure & interface over the years.
But this is hacker news, home of armchair pundits.
Mapbox comes to mind, but it is a proprietary service, not open source.
I guess I'm wondering why enabling people to build an entirely free/oss mapbox isn't near the top of their priority list.
If you want to render polished maps, you use Mapnik (developed outside, creators hired by Mapbox), probably creating your stylesheets in CartoCSS (developed by Mapbox) and using the friendly TileMill wrapper for prototyping (developed by Mapbox). If you want to do routing, you use OSRM (developed outside, creator hired by Mapbox). And so on.
So for your question, there absolutely is such an open source tool, and it's called Mapnik. Download it (maybe as part of TileMill) and have a play.