iPhone nav apps

Anyone here using iNavX for iphone 3G? If so what do you think? Is it worth the $50.00? How about tide and current apps, any suggestions?

<P>There’s a program called “Tides” that does tides…I had it for a little bit but got rid of it - it’s free, but I didn’t think it worked really well, and it seemed to be geared more towards beaches than ports.</P>