The support is amazing the system is extrememly customisable and reliable.
allt he plugins etc work right out of the box (unlike virtuemart). New features are being added all the time and the free version is better than many other e-commerce paid-for versions out there!
Used this extension to make 2 identical menu modules (except one with an extra menu item for "My Acccount Details"). Set both of these modules in the same positon, but make one visible to only registered users, and the other to anyone who is not signed in. Problem solved!
Should be core really! :)
It's very powerful in some respects, but seems to lack some very key features, such as the ability to automatically change the product image when you select an attribute such as different colours. It's possible to get this working through a hack, but every other e-commerce system i've used has this feature natively.
On the plus side there are a lot of plugins available for VM, due to its popularity. Though I don't know why it got so popular in the first place!
There are much better e-commerce solutions out there. The best I found were Magento and Hikashop.