If I had my time again, I would 1000% do it all over again, however, I take major issue with several aspects of my trip.
The single biggest positive was the people. We had a large group of nearly 50 people and I honestly enjoyed meeting each and every person. As a solo traveler, I found it extremely easy to make friends, as all the other solo travelers were just as chatty and eager to meet people. The super intense environment, where you were with each other constantly, meant that by the end I felt like I'd known everyone for months not weeks. My little squad (who will probably be reading this) are possibly the sweetest bunch of girls (sorry, older ladies ;)) I have ever met. I think I would have struggled to tolerate spending sooooo much time together with any other group of people. They were all legends and a joy to be around.
That being said, if I hadn't been so lucky as to get a lovely bunch of people, the trip could easily have been quite unenjoyable! The tour manager didn't really organise any sort of mingling activities or group games and had a rather short temper leaving several people rather upset. Some of the staff at the Contiki stays treated it like a holiday with their friends rather than a job, sending us off so they could swim and drink. The food was all relatively sub-par, especially the Parisian dinner which we paid a significant amount for. In retrospect, the trip was very poor value for money overall. Entry wasn't paid into any of the advertised attractions and these were all rather costly. The hotels and campsites were clean enough however after paying such a large sum of money (which didn't appear to spent elsewhere) you'd expect nicer accommodation. I was left trying to calculate where on earth all my money had been spent! As it turns out, it wasn't even significantly spent of wages to the tour leader or bus driver because you're still expected to tip!
Negativity aside, all the countries you go to are gorgeous and leave you really feeling like you've ticked a lot off the bucket list. Apart from Barcelona, I felt like we had sufficient time in each place and it wasn't overly rushed. Despite my complaints, I wish I had stayed on for Greek Week as I had major FOMO getting everyone's pictures and they all said it was the best part!
My advice would be to do it. You're not signing up for a budget holiday and if you're like me, some stuff will really annoy you but if don't complain and stay a positive polly it will be the best two weeks everrrr.