I haven't noticed Yahoo directory helped my main google serps yet. But it is one-month old website and those links still keep coming in so they need more time to prove themselfs. In my opinion it was a good choice but time will show if it is really the case.

I can add that i see now that Yahoo search uses directory description and title in serps not original meta tag title and description. So before adding the site make sure that your description is accurate.

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Cnc Machine shop equipment
Used Waters hplc
Zapiski