I have used it twice to get £147.18 and £157.76 off two holidays this year. You have to wait a very long time to get the money - around 8-12 weeks after the holiday takes place - but for more than the Welcome Home voucher's £100 I think it's worth it. It saves having to book by phone as well to get the discount as the £100 voucher can't be used online. If your holiday is relatively local and so costs less than the amount needed to get £100 of cashback then the voucher would still be a better deal.

You just book as a clickthrough through the link below to get a variable amount of cashback off any holiday. There are no restrictions on which holidays you can get the cashback on either - unlike the £100 vouchers which can't be used on Festive holidays. It is critical that you use the clickthrough to book the holiday in one sitting at your web browser or your booking won't be tracked and you won't get the cashback down the line.

https://www.quidco.com/just-you/ 

The rate varies over time. The highest I have seen is 8%, the lowest 4%, and it's currently 6% as of the time of writing.

All that's happening is you are getting some of the travel agent cut that they would otherwise get if you don't book directly with Just You.