i'm just waiting for shakedown to chime in on the modded Vox wah that he has.

prepare for an enthusiastic reccomendation.
lol im not pickin on you benny, im just an ass sometimes...
on a real note... i would say don't buy the digital pedal, it will probably be a fun toy for a while but it might not be something you really want or need once you know how to dial in those different tones using the controls on the amp/guitar. if you were to buy a pedal i would suggest a nice overdrive like a Tubescreamer from Ibanez or a Bluesdriver from BOSS for relatively cheap and good-sounding options.
my roommate has a crybaby and i get to mess around with it every now and then. they are a lot of fun but i haven't played with it enough to say that is useful for me, i just can't coordinate my foot rhythms while i'm trying to think melodically and do some texturing with my hands. although i'm sure with practice anything is possible for anyone. i guess its just like driving a car. btw, i love what jerry garcia could do with a wah pedal.
so yeah, definitely give anything you consider buying an extensive test-drive at one of those super guitar stores cuz they have a huge selection and are usually willing to let you fuck around for a while. do side-by-side comparisons until you are pleased with how you are about to spend your money.
that's my really long 2 cents. good luck on your tone search.
PEACE,
G