With dreamweaver cs3, I don't think spry has any server side validation. I think it has javascript pop up error messages.
Does Validation toolkit have customisable pop up error messages or something equivalent.e.g. Whenb you use dreamweaver javascript validation, all you get is that grey box that tells you you have errors in the form. I have seen much nicer customised pop up messages and interactive forms on various websites. Does validation toolkit give you control of the design of the server-side error messages?