I agree
I think a working knowledge of php and mysql really helps when using Webassist products, and tailoring them with a little bit of hand-coding really shows their worth.
There are some things I have done with ecart, such as managing coupons and offers via a web interface, or inventory control, that can't be done using the wizards alone, but I would have probably not even attempted them were it not for the infrastructure of ecart.
Wizards are great, but knowing what they do, the how and the why, is the key.
Even seasoned developers could save a great deal of time.