It really comes down to "if you want it then it's worth it". Functionally there's no need for one over a well made $90 forged lower. Functionality isn't why most people buy billet though.
I guess should have put a disclaimer in there. I have two Mega forged lowers and I'm picking up their ambi billet set just because (once I find one). Fit, finish, machining and details on their forged and billet stuff is outstanding.
There is no perfection. LaRue makes a helluva rifle, so does LWRC, Knights Armament, Daniel Defense, Wilson Combat, and a few others. :-) PERFECTION ....well.....her name was Sandy, and I should have never tried to do her AND her sister.....:-)
mega billet is what every ar enthusiast should want. even their forged ones are so damn consistent in quality. i just had to buy another set yesterday.
Hell yes they're worth it. I have a mega upper and lower, and they are utterly flawless. I don't think any other company approaches their level of aesthetic and cosmetic perfection. Perfect machining, finishing, and anodizing.
As for function, they work just the same as any other AR receiver set.