Hey, look at this thread from the Meta Board (by theymos himself): grin is now accepted for forum payments

If you read the post, you'll understand that our admin endorses it and apparently, there's a really high chance that it will be successful after a few months of liquidity (since there's only a few exchange had listed Grin).
As far as I know, there's one (can't say successful) coin that was endorsed by him that was pumped a lot and made some millionaires.
This will surely be the case to Grin on the first few months/year of release, but will not reach as high as Bitcoin's price due to its design (flaws?).

Personally, it's worth the time and money to mine a few before everyone join the inevitable bandwagon hype.

Right, and if you're into trading.... you know that "overhyped" is a very good sign.