Good points about security, BuddahBoy. The x-cart/joomla connector I referred to earlier isn't actually a Joomla component, rather, it allows both the applications to run independently, but seamlessly handles session management, synchronizes user registration between both systems, and allows all Joomla and X-cart data to be accessible from either system.
This actually appealed to me, since it would be allowing Joomla to do what it does best, with the ability to harness the growing number of module/component contributions, and leaving x-cart to handle what it does best as well.
I am in the process of setting up a joomla/x-cart website. The approach I used was to find a clean tableless Joomla template to use as a framework for my x-cart skin. With a little tweaking, There is now a seamless transition between both the joomla and x-cart portions of the site without noticing the switch [apart from change in directory] Definitely worth the time and effort, imho.
On my joomla pages, I created a module for x-cart login, so I am bypassing the joomla user registration completely and relying totally on x-cart for this. Hence, while the user syncrhonization part of the joomla/x-cart connector might not be that crucial for me, I think that being able to display a minicart, featured products, and access x-cart variables on joomla pages would add immense value for my needs, and likely the needs of many others who need more content management in their lives