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.
Very usable overall, quick to find information and conduct analysis for example of how a price of content is performing on Bing search. User interface is a bit clunky at times but easy enough once you get used to it.
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!