Purchased used and used on a daily basis on a 2015 Macbook Pro 15.

For data storage (documents, multimedia files, etc.), the speed is great.

If someone is thinking of buying it to run virtual machines from it, it's better to reconsider. It is doable but the speed will not be comparable to running the same VM from the internal SSD (or from an external SSD in a "good" enclosure). I repeat, it IS doable, I tried and compared the same Win10 VM with Parallels Desktop but for my standards, it is quite slow.

I recommend formatting it to HFS+ (Mac OS Extended - Journaled).

Recommended for people who want 256GB data storage without carrying a hard drive or dealing with USB sticks. For those who intend to use it for VMs, I would recommend an SSD in a "good" USB3 enclosure (google UASP), it will be cheaper for the same capacity.