Just update my alpha 7b to alpha 7c without major problems.
I had to remove Discount, VAT cause of the new checkout api.
I will work on the update of the VAT module, I wish the discount and the coupon module will have some maintainers too 
I disable inventory api and simplestock too for security. I will wait the next version when a certified compatibility with alpha 7c will be provided.
Except the "checkout module" that need update to work, The only error I had was with the catalog displaying, I had the theme_ functions of the catalog in my template.php and I saw that they changed a little. So, for people that redefined these function to theme their catalog, don't forget to take the new theme_ functions and modify them.
The catalog grid module have the same problem and need an update.
I test the new version since 1 hour, and.... congratulation, there are some very good new feature and interface improvement. I list some that Ryan forgot 
- Display the attribute on the cart block
- Display the majored price or the full price for attributes list (it's a new admin option)
- You can list products by price without error
- There is a new field when you adjust attributes, it's the cost price

I certainly forgot some improvement too but the work accomplished is awesome for a new married people 



