One feature that I use in a competitive product (Active Purchase from Active Modules) is their "Custom Action" support. Basically, this allows a developer like me to hook into the "Order Paid" event before the user's email is sent out and access the order's object model to tweak the email and save stuff in the database, etc. 

The store admin UI is pretty simple. Just one text edit field per product where you specify a Class and Assembly name, for example:

GenerateLicenseKey, CompanionSoftware.ActivePurchase.CustomActions

The class implements one method:

public void ProcessOrderAction(int ModuleId, int PortalId, Guid OrderId)

Specifically, I use this to dynamically create a license key for the products that a user has purchased based on their name and email address. I add this information to a a Note field on their confirmation email and store the information in a database table so users can retrieve their keys themselves from my website without any help from me.

A feature similar to this in AliCommerce would be a welcome addition.

Larry Daniele
Companion Software