I watch CMC religiously, (which results in me having heart failure every time NXT wobbles by 1%.....
)
Market cap isn't a perfect way to judge a crypto-systems success, but if does give a relatively good indication.
Keeping an eye on the data from CMC also allows you to spot obvious scams....like ABC and its regular pump pattern, which is so obviously one big buy made at the same time each day, with no other demand.