In the enterprise space things like this (eg, FusionIO cards) are used for everything IO intensive where the IO payloads don't fit into RAM. Eg, virtual server hosts, large size DB servers.
That depends on how sturdy these cards end up being. But, otherwise I agree.
Newest Macbook Pros have read/write speeds of about 900 MB/s, so they're only a factor of 2 slower than the ones from OP. And that has its use cases. For example, opening a big iPhoto library and browsing through photos, working with 1080p movies in iMovie/Final Cut Pro, having a bigger iTunes library. All of these will benefit of blazing fast storage.
Don't forget that we are currently moving over to 4K and higher resolutions, and that requires a ton of data.
Insane gaming rigs, maybe even servers (CDN's, content servers, etc...) if they can stand up to thrashing and take a beating.