It is more of a silent registrar / hosting. I have seen the name Gandi on hosting forums only once or twice. Possibly no one complained about them. There was no praise either. It could be possible that they are popular in some particular region.
In short, Gandi sound dependable. After all, they have been around all these years without much bad press. But there are other options like Namecheap which are quite good and affordable.
[*]1. They are cheap and affordable.
[*]2. They have satisfying amount of domains.
[*]3. You get free 2 mailboxes along with your domain for free
[*]4. They are not that well known, meaning they have less attackers (?)
[*]5. They just _gud_