SATA-1 may limit the maximum transfer rate of a fast SSD somewhat, but it won't affect the near-zero seek time and therefore the random I/O performance benefits of an SSD. So it depends on whether you're looking for benefits in, for example, load times (lots of random I/Os, should give benefits even with SATA-1) or in big file copy operations (you'll see benefits, but perhaps not as much as with SATA-2).