For real life usage (which differs a bit from a raw benchmark - even awesome benchmarks that try to measure things directly relevant to real life usage) the shipping MacBook Air with SSD are so much faster than anything with a spinning hard drive it's really amazing.
You have to spend twice to three times as much on a really fast iMac or Mac Pro to match the speeds of an Air that is switching amongst 5 or 10 programs that are not CPU bound. The SSD doesn't make things like processing video effects, calculating the layout of a 500 page document when you change styles or fonts, or downloading / uploading large files. SSD does make all those fractions to tens of a second waiting for a program to launch, switching tasks, firing up a calendar to look something up amazingly faster.
If you do things like compile code in Xcode - the differences can be astounding since there may be a thousand header files that need to be read, thousands of .o files generated before the linker will assemble a binary. Ten or 100 to one speedups are not unusual.
I guess my longwinded point is stock SSD from Apple are well tuned for the Mac they live in and are very competitive with anything else on the market. That fraction slower than the best benchmarking drives is also dwarfed by how much faster and system with better than average SSD are over spinning HD. The vast majority of the time a user is waiting for their mac is where SSD accelerate the user experience on a mac.
Also keep in mind that engineering tradeoffs that yield the fastest SSD drives also wear out the FLASH chips fastest. The drives Apple is shipping are likely tuned / specified to last for the 3-5 years of heavy IO that Apple users generally subject products. Apple will be on the hook for the subset of users that have AppleCare if the SSD fail in large numbers within 3 years of purchase. There's not a lot of good data yet on how these devices fare 2 years down the road performance or durability wise, but I'm certain a lot of work has gone into the SSD that have made the cut.