The benchmarks of SSDs like the Intel 750 suggest speeds approaching those of RAM-Disks.
The problem of course is, does this have that much value for consumers, who mostly do read-heavy applications (probably the most important benchmark then would be the Read @ 4k, probably at queue depths of 1 and 2. The big advantage I see is mostly in the field of sequential benchmarks, where we have seen huge leaps in terms of performance.
Boot speed and "application smoothness" don't seem to be improving that much.
It's mostly storage intensive stuff that sees the benefit, although I suppose if it's super write intensive, then an SLC SSD or perhaps a RAM Disk is still needed.