I am also tempted, and have had an lingering desire for an M60 for over a decade now.
Here are some of the factors I've been weighing...
Plusses:
There hasn't been a new transferable MG registered for 22 years.
(like old coins, etc. they are collectible)
I've heard that the price for these beauties, on the market, has been increasing by about 10% per annum. (you can argue the monies are invested, and not just spent)
If the SHTF, being able to "rock-n-roll" could come in handy.
Emptying a mag with one is darned fun, and always brings me a smile.
Minuses:
Keeping it on the target after the first round gets out, can be a real challenge.
They are ammo pigs. The typical assault rifle or SMG (M4, real AK, MP5, etc) will empty their magazine in under 15 seconds, at which time you get to stop and reload. Regardless of money, every round takes up space and weight inside your bag. I also suggest high quality factory ammo. Otherwise one squib could really ruin your day.
They are beaucoup $$. If you ain't got it, finding a really good mutual fund for saving up is probably the way to go.
The beast is registered. You will moved to the top of the short list for that proverbial knock on the door in the middle of the night.
You break it, you may be SOL. I don't know if you could get the receiver re-forged, machined, and still keep the same serial number.
The CLEO could deny you and you get to change that answer on your
next LTC renewal. The irony in the MG permit is that it doesn't matter all that much. The CLEO also has to sign off on whatever you actually decide to buy.
My conclusions:
The two things stopping me from getting one are the fear of the CLEO turning me down (on either occasion) and the $$ that I don't have.
In reality, the Barrett M82A1 looks more reachable, and is therefore higher on my wish list.