Well
Accuracy is good enough. I don't think the cartridge is any more or less accurate than 5.56. It's the guns and ammo and that make any difference there is. That being said, the vast majority of ARs will handily out shoot the vast majority of AKs chambered in 5.45.
Range. More or less a 300 meter cartridge.
Recoil is mild, on the same order as 5.56. IMO the AK platform recoils more than the AR.
Terminal performance is questionable. Truthfully, I think it is as small and slow as you can go and still have something that probably works (the bare minimum if even that). The whole yawing bullet thingy doesn't totally make up for it's small size. Let's put it this way, I have no qualms about shooting deer with the 7.62x39, but there's no way in hell I'd ever take my 5.45 hunting (unless it was for ground hogs).
Ammo prices are tricky. Right now it is cheaper than other stuff but slowly climbing. If the supply of surplus gets cut, look out. If things stabilize, and more comes in, prices might very well come down.
Should I worry about availabity of 5.45 in future?
Yes you should. The problem isn't lack of 5.45 in world, but rather stupid laws that keep it from being readily imported.
I have an Interarms Tantal. It is a very nicely made AK, but I am rather underwhelmed. If I had to do it over, I would not have bought it.