To be fair to Rennes, the triangular concourse over the station was part of the old new station (1992), and remained largely intact and in use throughout. The new bits wrap round it and replace the old new north and south station buildings. I guess it's meant to look sexy and modern, but unfortunately it reminds me of a certain kind of 1960s sci-fi novel covers.
Yes, I can see why it wouldnt be everyone's cup of tea in that respect, and the ethos does quite strongly tend towards the very modern in the designs that are put forward. That said, mixing the historic with the new can be achieved, as the recent renovation of the Art Deco-inspired masterpiece Saint Brieuc station showed, a well-executed brief that certainly contributed to its 2nd place in the most recent French Best Stations competition.
Going back to Rennes, I guess my immediate colleagues and I tend to be more focused on what it does rather than how it looks - and there is no denying when you look at the videos that it does an awful lot in many ways, in terms of the passenger facilities, the integration opportunities with other modes, the wide range of commercial units available on site, the accessibility, and the associated regeneration of the surrounding area.
Certainly feedback from users of all of the above has tended to be very positive, which is encouraging.