In theory: A driver that's actually open source allows it to be ported to future versions of the Linux kernel as well as other kernels such as FreeBSD, giving y

In theory: A driver that's actually open source allows it to be ported to future versions of the Linux kernel as well as other kernels such as FreeBSD, giving you some level of guarantee that you'll be able to use the hardware for the full extent of its physical life. In practice: Even ignoring NVIDIA's insistence on proprietary drivers, other manufacturers have already succeeded in making drivers that are technically "open source" with unreadable source code full of opaque logic and magic constants maintained by a kernel dev who has had to sign an NDA for the privilege of maintaining the driver, so the code isn't any more likely to survive a major kernel redesign (or perhaps a shift to a different operating system) than a proprietary driver would be, unless the manufacturer remains interested in actively supporting the device.