WeTransfer made it impossibly easy and efficient to Transfer files. They focus and they excel, they don't really host your files, they transfer them. Your files, if on the free plan, have a 7-day lifespan. The receiver gets a link and you get to know when they downloaded it, simple and great.
The interface is usable for no tech-savvy users (this is where many Cloud services fail because your client will need an account on the service, install a client, etc). In fact, neither you or your client need an account to transfer your files, you just need a link generated by the platform.
The downloading and uploading speed is incredible, even in places with poorer connections. Gone are the days of USB sticks, trash on your Cloud accounts, emails or the client saying "I didn't get it" when they did. I often share heavy files like RAW files and .psd projects and this tool has proved wonders. Like a professional mediator between you and your client. "Here is his work, please download it".
This company has also a great eye on design, proved by their beautiful backgrounds, super simple interface and now on the great stories featured on WePresent.
The mobile app can be buggy if you are dealing with a big file. This is not a problem but can happen, in a remote scenario, that you delete the mail with the link and your client does the same then the link is forever lost. It could be great to retrieve a log of the active links under my mail, for example, I could send an email to WeTransfer with a subject of "Log" and I will be replied with my current links (I understand the security issues involved).
Many people seem to be a concern on how the company handles the privacy and security of the files shared, in the case of sharing highly-confidential files I would think it twice.