Basically it seems like the line hasn't been at all well treated by  the sillicon era.

Black is relying on short term activity/tricks to offset his space disadvantage. But if white is very accurate black does seem to end up in some slightly depressing positions - Golubev's excellent KID book has a game covering this. 

Is the line complex enough to play vs 'random' people with decent success? Yes. Thus all those games in the 90's. 

Against someone prepared with sillicon/a database though it suddenly gets much less tempting - especially as the lines are fairly forced/'straight line' so its relatively easy for white to prepare and hard for black to generate chaos.
(much harder than say the 7.. Nc6 main line.).

Survivable with the right attitude/care perhaps but the KID isn't the easiest way to get a solid, slightly worse position!

The standard Glek is 7. 0-0 ed 8. Nxd4 Re8 9. f3 Nc6, whereupon 10. Be3 Nh5 11. Qd2 has, as far as I know, long been commonly regarded as leading to a slight advantage for White.