Likes:
Even coming in second is usually beneficial enough to justify the production spent on a project. They did a good job making sure the rewards of trying to compete would be worth it should you be in first or second.
The projects are a neat concept for multiplayer, because if you have no need to try and compete for the prizes of contributing, then you can use the duration of the competition to try and attack opponents at a time when they are unlikely to be building as many units as usual.
Dislikes:
International Games is a huge issue for cultural victory. Get 1st? Much easier time winning cultural victory. Get 2nd? Well, without that Tourism boost, it's going to be quite a bit tougher. International Games is the only project (and I've already competed in all-three) that really seems to be make-or-break, as the ISS comes late enough that it may save you in a close-spot but really isn't going to catch you up enough if you aren't already in the running for science victories.
I only got notifications at 35% done on the projects. That seems odd. Why not 25%, 50%, and 75%? Could have been just how much I contributed and what not, but I only saw one notification informing me how much of the project was completed each time, and always at 35%.