One indicator of possible success would be seeing its major competitor, the Financial Times, follow it. I'd have to wonder if Google Finance is even in the same business, e.g. unlike the WSJ or FT it doesn't charge "subscribers" for regular content at all.

The WSJ has some free articles and lots more if it thinks the link is redirected through Google (perhaps the Pro Edition articles don't allow that???), the FT only allows you to read 3 articles per month without free registration, then at allows a bit more than a dozen per month the last time I checked.

One thing to look for is non-delayed market info, you have to pay a lot more to get it without a 15 minute or whatever delay.