I've been using website testing tools for quite a number of years, and I've literally never heard anyone refer to GWO's testing setup as easier. GWO was an implementation nightmare.
Every test had a distinct set of JavaScript tags that had to be individually implemented for every single test. You had to place the scripts on each of the pages, and then verify that all 3+ of the script snippets are in the correct place (and if your test failed validation, you couldn't launch it). Making changes on the fly was difficult. If you misconfigured your goal, your data was forever lost (and you couldn't know if you misconfigured your goal until the data came through, and that wasn't in real time).
Contrasted with Optimizely, for every project, there's a single global JavaScript snippet that goes everywhere. No need to change snippets for every test. You can configure your tests from one place. And, for page-view level goals, you can add goals after an experiment starts, and they'll retroactively apply experiment data.
For a simple test, you can implement an Optimizely experiment in less than 5 minutes and feel assured that everything is working immediately, since it has real time data. If you need more power or complexity, it's there, but if you don't need it, it doesn't get in the way.
(Disclosure: I've been using Optimizely for nearly 4 years and recently spoke at their user conference.)