Most of the Eldar armies I see run two or three falcons. This vehicle fully tooled out is a monster of a machine. It takes a really lucky roll to kill one of these machines. I faced this army for the first time and thou it seems like a great army. The army I run had no problem with it and I dont see one in the future either. Thou, looking at 87 marines on the board is something a small army is unable to handle in the first place.
Thou, it is a great army for all kinds of reason. Main thing is point denail and yes this army can do that. You might blow a weapon off and on his turn he boost to the other side of the board behind cover. This sucks unless you have some way of getting to him.
I myself have even thought about running a army around this theme. Falcons on ebay are not that costly and getting three would be easy. Two more and convert for the heavyies. Now all I would need is the codex and some troops. Thou, I would think of fielding as many of the vehicles as I could.