Worth of premium directories!

[shannon]

Now a days there are plenty of directory projects out in the market,and some of the companies charge big money to list their site into their directory.
So far i haven't had much luck with free directories but I know these free sites can sometimes be quiet useful .
If i has to invest in one of the pay sites which one offer the most ,deep or immediate impact ?

Thanks

[iGuides]

I would recommend you Aviva's Strongest Directories list here Strongest Directories All premium paid directories are listed there according to their PageStrengths