I have been using ONE for a year, and fairly happy with it. It does struggle with projecting the right theta decay values for calendar spreads, but that is a limitation of all softwares due to the difference in implied volatility between the long and short option. Otherwise I find it very useful.
I know there was a big exodus away from optionvue last year, after the software changed ownership and management. From what i am led to believe based on reports in other forums, there was difficulty in predicting behaviours of put butterflies, it may have been fixed now.
@tom : which of the options of optionvue do you recommend for retail investors since they have several choices ?