Julian G4ILO mentions his enjoyment of PSK31 on HF on his blog today. Although I've had a fair few QSOs and some good DX with this mode over the years, I'm not a great fan of it.
It's a while since I've tried PSK31 on HF. Maybe next week when the grandchildren go home I'll give it another go.
The ARRL reports that Varicode, as used in PSK31, has now been officially recognised by the ITU. See http://www.arrl.org/news/amateur-created-varicode-adopted-as-itu-recommendation .