Yes it's great. By my rough math, a GTX 1070 earns approximately $36USD/month mining Siacoins. You will lose a negligible amount off your ETH but it's worth it IMO. My one issue with this is that it overheated my top GTX 1070 card. I guess it made it work too hard and it couldn't handle the heat. So what I did was put in "dhci 0,50" and that effectively made it so that only my bottom GPU is mining Siacoins.
I haven't figured out how to cash out or convert the Siacoins to ETH but I'm sure it can't be that hard.