While the number is mindblowing its usability entirely depends on how the track creator itself will be. If it is as simple as GT5's then it's a large canvas without having a brush, the tools. On the other hand, if it is very well made then it'd a huge deal, with almost complete control of the circuit (or point to point layout) and of the surroundings (buildings, lightning), especially if the work can be shared with other users.
That means the track creator itself is what is of the essence, not the area available. Creations could be either a huge random circuit or a simplified Isle of Man, depending on the tools.
Personally I'm not expecting the freedom that only can be achieved on a PC and with technical knowledge, so not a tool made just for track creation but 3dsMax, a mouse and scanning of the actual circuit, though if PD itself hypes this so much then I expect to be able to recreate the layout of famous tracks and roads in a simplified manner. That means no bumps, no complete control of elevation changes, no pictures of real life buildings, etc., in short able to do laguna seca but not the corkscrew nor the the inclination on the left of the previous turn to it, or could do your local city but without the the actual buildings (on this last matter I hope we can use the already included in GT6's assets, like Rome and Tokyo buildings).
edit: And I really hope and almost expect that the GPS feature is tied to the course maker, so the layout got with the GPS can be tweaked (for example width and surface) and surroundings be added with the course maker. That would make much easier to recreate real life driving roads.
. Just bringing that up.
Then he didn't brake into the first corner... lol I then closed it.
