On our recent run up the NSW coast and during the race on Lake Macquarie we used OpenCpn largely because it runs quite happily on Linux. It proved itself easy to operate and I'd happily use it as an alternative to MaxSea which does not like Linux. SeaClear is also non Linux but I've never used it.
I know its a great debate but I still keep a paper chart at the nav station and mark our positions as we go along. The reality is however that in the conditions we experienced during that race GPS was a far more reliable system than manual fixes would have been. The good old fashioned Mark 1.0 Eyeball is all very well and good but when visibility is down to a boat length its nice to have a satellite.