We have started using Optimizely a few weeks ago and so far it has been very useful. The setup took just a few minutes. You just add their code to your website and are ready to start your experiments. You can A/B test literally everything on your website: button colors, CTA texts, website wording and much more.
There is no need to add any code for each experiment. You do everything through your dashboard and can even test the experiments in your browser. Once you publish an experiment it goes live and visible to your visitors.
The reports they provide are very easy to understand and help you make the right decisions.