Basically, it makes any unit using it an instant badass.
See, I love the Tau, except for the fact that underneath all that cool sci-fi armour, they're just Space Goats with Voldemort faces...
Yes. Yes it does.
+1 for the Space Goats with Voldemort faces. I personally like the Inquisition waaay more though. (more power than you can shake a stick at has its instant appeal).
Hey Whiskey... How big is a crisis suit, and how does it even work?
How big? Probably between 2 and 3.5 meters in height, maybe as much as 1000 kilograms mass, and probably a meter or two in width and depth.
How it works? No clue. You'd have to ask an Earth Caste scientist, and even you probably won't get an answer you'll understand (stupid xeno languages and heretical unhallowed xeno machines).
After all, the Imperium is more advanced than the Tau and arguably more advanced than the Eldar. It does feature weapons that are star-destroying (literally; look up M37 on Lexicanum, specifically the Occlusiad War).
The Imperium can even build what is technically a lightsaber: the Sollex-Aegis Energy Blade (Lexicanum is your friend).
It's pretty clear that I mean to imply that it's the greatest of all things when I added that there's nothing better. It's greatness rises above the greatness of all other objects. Snakes on a plane transcends comparison to mere cinema and your attempt at confining it to that medium with such a dumb remark is insulting.
If your being sarcastic about the supposed greatness of Snakes on a Plane, please stop. No one else thinks that SoaP is a good movie (I just realized that the acronym of the movie name spells 'soap'), so you're liable to be labelled a troll.