Booking on Transavia was pretty easy. Before you book though, read all the details.... its a budget airline so everything costs extra: baggage, food, drinks, picking a seat, etc. But as long as you know this, you can see if the cheap fare is worth it. For me, it was.
The planes are decent... the leg room was fine.... more than most US regional flights for sure. Very clean and the staff were super. Out flights were all on time.
The 2 big issues I had were boarding and check in (in Las Palmas.)
Regarding boarding... there is NO protocol. They basically decide they are ready to board and say "now boarding." Its a mad dash of people jostling in a huge crowd to be first. Very frustrating.
Second... check in. In Amsterdam (the hub) it was very easy and efficient. Several agents available to assist and get your bags checked. In Gran Canaria... horrible. They had 3 agents, but no defined lines and they wont start checking people in until exactly 2 hours before the flight time. So most people were there about 2.5 hrs early and a huge mass of people just stood in a messy mass until they "opened." Then it was a crazy fight to be in a line. Just way too efficient and causes so much frustration as people get annoyed with other people as they push in front of them in line.
Just remember its a budget experience. If you want to get to many places in Europe for cheap, its a good choice... far better than say Iberia Express or RyanAir. Just make sure you know the rules of the road.