This was discussed a little bit 6 days ago here by @rahvin84. I'd like to reiterate and warn users about the dangers of SPARC before you all start to spend GRC/ETH as transaction gas.

SPARC announced itself to our community on the subreddit a month ago, and linked us to their webpage. The webpage included scathing criticism of GRC, most of which was either outdated or factually incorrect regardless of when it was written. Their whitepaper was also riddled with errors, grammatical problems and formatting issues. Worse, they openly admitted on our sub that the whitepaper was outdated, despite an active ICO being ongoing.

Further, SPARC was just onto its second ICO phase. To make it appear like there was a lot of investor interest, they appear to have washed about USD$50,000 worth of ETH through their investment wallet. You can go trace the addresses yourself to check this, and Neuralminer has already done this.

On the other hand, they are very quick to reply to any emails and appear very friendly. I just advise significant caution. It is very easy for anyone to set up a 'dumb' ETH token (one with limited functionality beyond 'being a token').

As of now, you are unable to sell SPARC on any exchange. If you do withdraw it, be very careful that your ETH wallet of choice supports ERC20 tokens or your SPARC will be lost.

im currently waiting to see if they do backpay of credits ive gotten or credits i get from today forward.

They do not backpay credits, instead paying out your share of SPARC based on the extra credits you earned the past week. Payouts are scheduled for every Sunday, but they have not been consistent so it looks like the process is not yet automated. Alternatively, maybe they are waiting on all the project servers to come online to allow stats to be gathered before they pay out.