http://kotaku.com/it-takes-31-minutes-to-run-across-xenoblade-x-s-open-wo-1708403421

It took him ~31 minutes, and the transitions between continents seem somewhat seamless (there is a video in the link.)

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Some random math 

Assuming on Mira that you can run like 1.5 times faster and last longer at that speed than a human on Earth, it would mean that he ran  (let's assume average human runs 4.5 m/s over a span of a mile) around 7 m/s. Using that estimate we get 31.25 minutes*60 seconds/minute * 7 meters/second ~  13 km or 8 miles. That is a little bit more than Skyrim from one end to another (~ 4 - 5 miles.) 

31 minutes eh? That's pretty decent I guess :p
Now if we only could get a comparision for XC and XCX

Nice! Can't wait to play!

I would say a linear run from the bottom of the bionis to the top is longer to traverse because the areas are longer by the nature of the shape of the bionis' leg, thigh, back, etc. However, XCX obviously has much greater total area, even if we disregard depth of the world. And there are also two other continents not shown in this run across the world. 

Yeah I would assume so too, but just for the fun of it :p
I know there's a video about it out there somewhere.

XCX has already been said to be 5 times the size of XC

Certainly, a Skyrim character would take much longer to cross the world just because he can't sprint indefinitely (and not as quickly.) Still our brains calculate the size of something based on the speed we are going, so while it might not take us any longer to travel from end to end, we will still feel as if it is bigger because we know we are going faster. 

just 31 minutes?

I though the world would be 400 km^2.

So normal run speed it like 5min/km. So 31 minutes will be something about 6-8km. And the world isnt even a balanced place, the world is long drawn.
Even if it would be 7x7km for each direction (whats it not) that would be just 49 km^2.

So NOOOO way the world is 400 square miles.

GTA V takes ALOT longer to run through the whole map (like 1hour +).

So they lied about the world size?

The world is not 400 square kilometers. I made a thread a while back estimating the land size to be something like 100-150 square kilometers. The 400 square kilometer estimate probably includes oceans. 

Remember though, you run faster than a human on Earth because in Mira the gravitational acceleartion is smaller (so more energy goes a longer way) but not too small that you can't get enough friction. A human in Mira probably runs 1.5 times that of GTA V. 

Also this is not including the two northern continents. I expect this game to be 1.5 times - 2 times the size of GTA V. 

ok even if we say hes probl like 2min/km (which is really fast) ill do some calculation.

so from left to right it would be 15km. So 5km length for each continent and like 2km width for each should be realistic if you compare to the map. All continents are similar in size. So ill get 10km^2 per continent x 5 continents im still at 50km^2. Thats smaller then GTA and around same size as skyrim. I see no way this could be 200km^2. Then the character would run 30sek for 1 km which would be 120 km/h =75miles/hour. Thats unrealistic.

Square Kilometers is an area measurement, when you run through something you're obviously covering a very small part of its total area, just something to keep in mind