How much is it worth? Depends on A) where you bat him in the order, B) what his hit distribution looks like and C) what the rest of your offense looks like
I like John Kerins and Fred Carroll a bunch. Both hit triples, which their high speed rating lets them replicate in the sim, but the real benefit is that they'll take the extra base. If you have a good offense that puts a lot of balls in play and hits a lot of singles, doubles, triples, the value of high speed players rises in concurrence. I typically spend more on hitting than pitching and a big reason for this is because I favor the speedy guys (not just at C, but including C).