The same. Only works if the Macbook is standing in the same room as the router.
In the next room the sendrate shrinked down to 41,5 % on average and the RSSI also lost about 20 %.
Meaning the connection between the Macbook and the router is getting worse.
That also leads to an overproportional loss in internet bandwidth... down to 0.04 Mbit/s download! It doesn't matter if I have a contract about 10 or 20 Mbit/s download... and that's the important figure for me. That means it was down to 0,4 % of my average download bandwidth. Equals... internet is not usable any more.
When I tested it opened, it had perfect connections at the same time.
Just the clamshell-mode (closed mode) doesn't work.
Different wifi channels had small differences (max 1-2%) on average. Network mode changes from mixed over b, g, or n the same. n was up to 5% better with RSSI. After that the mixed mode worked the best. The other modes also had a loss of 50% in the sendrate in comparison with the mixed mode.
Additional wireless devices (bluetooth keyboard, 2.4 GHz mouse) didn't disturb more than 1%.
The wired external screen disturbed around 1-2% with open Macbook.
It also hasn't change after downloading the latest airport software.
Overall Apple should offer a kind of software update or an external antenna (usb-stick) to make sure the Clamshell Mode works in another room than where the router is standing. Otherwise it's not possible to work professionally. Not even email can be used properly.