I rode one for the first time last night.
I live in Estover and regularly meet up with friends in Plympton. Although I can drive, I sometimes get two buses at Ā£2 each. The combined journey times including waiting for one bus at Marsh Mills and walking between stops is about 30 minutes, but longer if I miss the Plympton bus from Marsh Mills to Ridgway.
Last night, there were no bikes at Asda, my closest base. Therefore I walked to Leigham (10 minutes )where there were 4 bikes available.
I then rode like a madman to The Ridgeway which took me 15 minutes, which worked out at Ā£2.25. Because i had a prepaid bundle I didn't pay the Ā£1 unlock fee.
All in all it worked for me on a dry evening. I saved money and didn't contribute to 'global warming' (neither of which cause me to lose much sleep in truth).
As an aside if you see an abandoned bike and return it to a bay you will be rewarded with bonus minutes.