I had originally subscribed to CML, but I recently dropped my subscription after using it less and less. For me, it just wasn't a match for my trading style. It was a fine tool for backtesting different options strategies based on historical stock price movement, or lack thereof. However, trade entry and exit were based on dates and gain/loss thresholds. So much of the SO-style trades are based on determining good entry points based on IV and earnings history and how prior cycles compare to one other. Even the SO index trades (VIX, SPX, RUT) factor market volatility in trade entry/exit decisions. You couldn't use CML to base trade entry on volatility based triggers.
For the SO-style trades, having the RV analysis tools (volatilityHQ, artoftrading) are by far the most important. Being able to easily & quickly generate RV charts for calendars and straddles, IV charts and earnings history is the most important thing. Going back a couple of years, it was so much more difficult to do this analysis than it is now.
IMO, if you are looking for a tool to help with you SO-style trades then CML is certainly not a "must have" - the RV tools are so much more useful for them. If you are looking to make other types of trades based on past history of stock price movement then you may find CML useful.