I don't think it is a 'nonissue'
I used to have an asus eee pc. Everyone would talk about the bad performance of netbooks but I used it as my work computer for 4months and it wasn't so bad except for flash performance (and this was on windows where flash is more optimized)
Flash intensive sites would make the thing stutter and watching high quality flash video was a big PIA. It made web surfing, one of the main uses for machines like these, not a full experience because some sites (I'm going to call out CNET here) like to be really Flash intensive.
The point is I think it is important to be aware of the 11" MBA's limits. They don't just include obvious things like video editing and 3d rendering. Most people will want to do their regular web surfing activities on this computer and they should know it might not perform exactly like higher end machines for some sites. And no flash 10.1 won't completely solve the problem. On my MBP the CPU is still at 75% watching youtube in HD.
This doesn't mean the MBA isn't a good machine but it isn't going to perform miracles either.