What does Optimizely do well? Optimizely is a fantastic tool for anyone looking to do basic (and some advanced) A/B testing and experience optimization on their websites. As data driven decision making is a crucial aspect to UI and UX decisions and improvements, Optimizely provides the rich data and customer insight you need.
What does Optimizely not do well? Compared to other, native tools, like Sitecore's Experience Optimization platform, Optimizely can become a bit clunky when trying to push experiences to production after they have won a test. With a more native platform, it can typically be set up to port the experience straight into production. But with a tool like Optimizely, you need to recreate that experience using your native platform.
What do you wish you had known about Optimizely before using? How much value there is to get out of A/B testing, and how easy it is to get started with Optimizely. The WYSIWYG platform makes it super simple to make changes and run tests on the fly, without any development or coding.
Have you used a competitor to Optimizely? If so, how does it compare? I've also used Monetate - which I found to be more costly for roughly the same feature set, especially when you consider what most companies are going to *actually* be using the platform for. I compare it to a Honda vs a Lexus. Will Honda accomplish most of what you are trying to achieve with the vehicle? Yes. Will you get more bells and whistles with a Lexus? Yes. Will you pay more for a Lexus? Yes. So really you have to decide how much those extra bells and whistles are worth and how much you're willing to pay for them.