Google Trends - A good tool for understanding seasonal content. It also displays results in a more visual way but presents much simpler results than Keyword Planner. It shows interest in keywords and search queries, but doesn't give you the exact number of searches or your organic position. It is definitely worth having with Keyword Planner, but I wouldn't recommend only using Trends.
High ranking metrics will result in getting your site on the top position of several charts such as Top Alexa sites, Top WOT sites and so more. People usually go through these lists to discover new sites and hence you will be getting referral traffic as well. Who knows? Some of those traffic may be your next big client or loyal reader of your blog.