RAID-0 will increase the transfer rate of the drives, but not the access time.
That means it will be of the greatest benefit when you're doing work that requires reading or writing a relatively small number of fairly big files, such as when you're copying some large files or running a program that reads or writes files such as photo or video editing (note that simply playing music or movies doesn't require a very fast transfer rate).
It will be of the least benefit when doing something that reads a lot of relatively small files, as in booting the system or starting up programs.
Where RAID0 makes the biggest difference it in reading and writing large files. If you have a PC with just an OS and office program on it, there will be no noticeable speed difference between a single SSD and several in RAID0. Install a modern game like Battlefield 3 or Call of Duty Blacks Ops II, and you will notice a huge difference -- this is because contemporary games have huge files, some, such as texture files, can be several hundred mb in size. Reading a large file with one SSD will occur at whatever speed (SATA, SATA2, SATA 6gbps) you have configured/supported. The difference with four drives in RAID0 is that instead of sucking a 200mb file with a single straw, you use four straws. [a single 200mb file accessed with four drives in RAID0 will occur at the same speed as if you had a single drive and were loading a 50gb file]
Accessing a file off a single Intel x25-m will occur at the same speed as having four of them in RAID0. 'File access' means the speed in which it takes for the hard drive to get from where it is, then read the FAT table, then move to where it needs to be. It is of marginal use in comparing SSD drives together, since they all operate very fast (versus a traditional spinning drive that has to physically move its head).
The other difference will be OS related -- if you have four 80gb drives in raid0 they will appear to your operating system as a single 320gb drive. this might appeal to you if dont want to mess around with d:\ e:\ f:\ drives and juggling files between them.