Yep. I recommend you set it so one is like "MySSD" and "MySSD 5GHZ", that's how I do it. Then I just make sure that "MySSD 5GHZ" is my preferred wireless and that it falls back to "MySSD" only if for some reason the 5ghz band is down....
Yes, I tried it and it seems to work OK.
Some oddities :
1. I have an Extreme as the router with some 1st gen Expresses and 1x new Express. Before I made any changes, the Airport Utility correctly displayed the tree with the Extreme at the top. Now, the new Express is at the top "connected" to the Internet (no) and the Extreme underneath (ha)
2. I tried the 5Ghz add-on, but it was confusing, so I have given the bands 2 different names and set the order with the 5Ghz one first. That way I can use the 5Ghz named one also in the Expresses that ONLY use 5Ghz and keep the current name for the 2.4Ghz ones. So far so good.
Yes, I am sitting 10 feet away from the new Express and I am connecting at 300Mbps on 5Ghz. Success !!!!
Cheers
3rd oddity :
The MBA would rather connect to an older Express at 5Ghz one floor down at 60Mbps than the Extreme one floor up at 5Ghz and 2.4Ghz, even though it's nearer. If I go 1 floor up, then the connection is to the Extreme at 300Mbps and 5Ghz.
Carrying the open MBA 1 floor down preserves the Extreme connection (nominally at 300Mbps), but sleep/re-awake switches again to the Express.
Nope - It's gone back to the Exteme at 180Mbps - so logical after all.