Yep. Mailed off four international shipments today with Forever stamps. It's actually really hard to find stamps these days with face values. 1,2,3,4,5,10 cent stamps, $1, $2, $5 stamps, and the priority and express stamps are just about it and not every post office keeps a decent supply in stock.
The Forever stamp is the same as any other stamp (in modern day use), except it has a "sliding value", i.e. it's face value will increase over time. The stamp is assessed at the current rate on the day it is use, regardless of where it is going. You're paying for the postal surcharge, at the rate on that day, to the destination it is going. So as Trainwreck mentioned, the will increase in face value to 55c in a few more days. So if the rate to send your letter to Australia is $1.10, then 2 Forever Stamps after the 27th will get you there.