It does all of the above, and it is slowly catching on here. The issue is cost for Australian coins and shipping it costs about $18 to slab and grade a coin, plus freight. For that reason you need to send a few at once,I was quoted by a local agent that each coin would cost close to $30 - $35 by the time I got it back as you need to pay postage both ways.
The biggest winner I feel is that it does standardize "that" particular coin it has been set. So in the S/H market or dealer market it has a standard attached to it. The choice then becomes if you agree and are prepared to pay that premium and a closer book value. As a real rough example -
If you had a CH/UNC (MS63+) 1956 Penny just to pick a date.
Book value - $250
Ebay Unslabbed - average is about $50
If it was slabbed it would go closer to $150 - $200
So the extra $30 is probably worth it for a better return. Again depending on the buyers and preferences. Also you would not bother with everyday circulated coins unless they were high value ie - 1925 Penny. However the under educated buyer may pay a little extra thinking the grade is a little stronger than what the seller is offering it at and vice a versa.
My goal is buy quality coins at the best price possible and then get them slabbed for protection and hopefully by the time it really catches on here 5-10yrs I will have a very worthy collection.
As for grading modern bullion and numismatics I do not see this catching on here for a while, but there is definitely a bigger premium in the resale market for these coins in the US. If you can get a PF70 grading on a modern coin they call it a first strike issue, while not technically correct in Australia as we do not grade our bullion coins as Proofs but the quality is so high they get these grades. Here is an example of a modern numismatic being slabbed and he relative price - 280650735010
I like them but like everything they have their good and bad points. I would also only stick with the name graders and keep away from the rest. Just because it is slabbed by just anyone does not carry a lot of weight.