I tried it and it immediately cuts my ptbb/100 in half. If you play 16 you don't have time to spectate the other tables anyway... but i play around 8 most of the time, and I like to know how the table dynamic works and to pick up reads and make notes even when I'm not in the hand.
Lately I've tried to go back to 4 tables cascading - preferrably ultra-short handed to HU. It's quite likely less $/hour, but I still have to learn a lot about the game, and this helps me analyze the tables better. I don't get bored either.
For the bonus at FT I sometimes stack 16-20 25NL tables... only way to make it without carpal tunnel for me - But it doesn't feel like playing poker to me... it's just a bunch of automated decisions. But I guess if you're good at interpreting the HUD and fast enough to look up recent hands and look at notes then I guess this is the best way if $/hr is what you're after. - $/hr is always nice, but for myself I think if I want to move up to 200NL at some point - which has been my goal from the get go I'd rather play less tables and try to pay more attention.