I like the software but it's overpriced and has some catches in contract.
I've used Optimizely for a year and I'm very disappointed.
They have a catch in contract where you need to send a written cancellation request 1 month in advance or else your $2,000 per month contract is automatically renewed for a year!
Now we can't get out of the contract for another year ($24,000) and we aren't using the product anymore.
We have switched to VWO and realized it's a far better product with better price.
For ~$800 a month (vs $2,000 on Optimizely) we got 3x more visitors and more features.
Consider alternatives like VWO, it will save a lot of money but you actually get the same and you'll avoid bad experience. I've used Optimizely for over a year and VWO for over 5 months