i have 2 Einsteins and i find them to be very reliable and built much more solidly than the older AB units. i have not yet tested the high speed flash duration of the units but it was a feature that i liked having if the need ever arises.
some other nice things about the Einsteins:
1/10 stop variation in power over a 9 stop range
ability to control power of multiple strobes via camera with the Cyber Commander unit
value vs quality (its just a good product for the cost compared to other brands)
i have also not had any issues using any type of modifier with them. i got the units when they were first released and i was aware that they were going to correct how modifiers were attached to the unit. as i understood it, occasionally a large/heavy modifier could "jump" off the unit so PCB planned to extend the length of the clasps that engaged the speedring that the modifier was attached to.
i have never had an issue with this and i have used up to a 36x48 softbox on these units. i do hope to get a 54x72 softbox in the future so at that point i might send the units back in to get them updated to handle the extra load.
bottom line is that i find the Einsteins to be well made, reliable, and very very versatile. but i would try to research how they perform at faster flash durations and if they are capable of what you need. the only other units i saw (online) photographers using to do such work were ProFotos...and they are beastly expensive.
Thats some piece of mind. One thing about my ancient novatron gear is its tough as nails. Fallen several feet, dropped kicked, battered but continues chugging.
I saw some broncolor/profoto stuff and its amazing but wayy out of my budget! Then I read stuff on Einstein and knew it was perfect.http://strobist.blogspot.com/2012/10/freezing-water-on-cheap-einstein.html