The ultimate way to season cast iron, per Cook's Illustrated
Short answer: it works
Is there a difference to other oils: Oh yes, it's like using nail varnish
So should I believe the hype: I'm afraid so
Concerns: Like glass, looks brittle (but probably isn't)
Tips: wipe off as much as humanly possible
Temp: Going over 350-400 is (probably) overkill. Has a very low smoke point.
No. of coats: As many as you like. But I wouldn't recommend more than one a day. I'd say do one coat a day (or week even), while using your pan, and take as many weeks/coats/tries as you like. If something sticks to it you can scrape it off with a metal spatula. Just like a girdle. In fact it is a girdle... just pan shaped. Remember, most foods unstick themselves if you are patient.
But will I be buying another bottle of flaxseed: probably not. It was a fun experiment and the results exceeded my expectations (so I'm glad I did it). But I'm getting really tired of babysitting my pans...
Conclusion: If you feel like it, go for it! But you'll probably end up using plain ol' Crisco/lard again in the long run:)
PS When people say "thin coat" what they really mean is "wipe it OFF". All of it.