I've spent a good amount of time re-building a client's store since the MP 3.0 upgrade. The patch applied this morning 3.0.3 fixed a few issues like the product pricing and bringing back PayPal Express configurations, but broke several others. I have now rebuilt my variable products, allowed the plugin to create all new store pages (3.0.2 allowed you to specify existing pages for cart and store) and various other items.
At this point, two issues remain which I cannot resolve on my own.
1) The Checkout function appears broken. The checkout button yields zero results other than refreshing the page. If I use my menu navigation to go to Checkout, it works. I rebuilt the menu to use the newly loaded checkout page, so this makes no sense that the in-process button would not also take you to the checkout page.
2) The PayPal Express integration appears to be broken as well and returns the following error message to a user. I did not change the PPE integration in anyway once it was brought back by applying the 3.0.3 patch.