Has anyone gone through the process of providing purchasable gift certificates
in version 4.0 ?

What do you mean purchasable? Do you mean adding them to your site for people to buy?

If so,

This is very easy.

1.Just add a product just as you would do any other product.

2. In the product editor you need to click the button that says "gift certificate", it is located around home page special etc...

3. Click save and that product is now a gift certificate.

4. To set the value, you just price it the same way as you did your other products.

I don't know if the cart is already set to know this... but I'd check off Free Shipping also

If set it up on my site and you do need to make sure that you set the FREE Shipping Up..

Cause trust me it will add the shippingif you don't...

EXAMPLE:

http://store.desertscrappers.com/index.asp...PROD&ProdID=902

Have Fun!