I always make sure that we are actively using Bing and Google. There is a tradeoff in your time when you use more tools, but there's also benefit in multiple perspectives. And don't forget that Bing is a very viable search engine that receives 500 million search queries each month. You may find that your business benefits from a relatively small amount of attention paid to Bing because search ranking there is easier (not easy, easier).
The user-interface isn't as friendly or appealing as Google's - very bland overall.
The way they present their Page Traffic report is a big turn-off. It's basically just a grid of numbers and arrows which is hard to interpret at a high level.
I think that Bing does a good job of being a competitive product in a space that has very basic and insanely complex products. While Bing isn't pretty, it gets the job done and also gets you the right tools in a simple and straight forward backend UI. The ability to place Bing ads, track SEO and see how your site is performing, all from one backend interface is awesome!
Frase gives a lot of content to use, but it doesn't give you the factors you need to rank. This is ultimately why we use SurferSEO over any other editor tool that is out there. The analytics are number one to the entire space.