Hi, thanks for the detailed descriptions. Most of the concerns you have are already addressed in the current version, except PayPal Express. Let me go one by one:
1. The top menu is floating, if you scroll down it should remain on top (at least in desktop view), it doesn't remain on top in mobile view and I'll create an issue.
2. That is correct, we'll include it in our roadmap.
3. For the multi attribute products, check the following sample product in our demo: http://demo.virtocommerce.com/en-us/electronics/audio/apple-ipod-shuffle
Also look at how it is configured at the backend. As you can see it has 2 properties, color and size that are dependent on each other and also have inventory values.
Let me know if you have more questions and I'll be happy yo assist.
We implemented more advanced template engine as well as PayPal integration.