First I want to say that W3TC is awesome and has helped me to get my site performance ranking way up, so great job!
I'm having an issue with Woocommerce cart status updating with W3TC though as it seems that W3TC caches the cart status on pages and doesn't update it appropriately when changes occur in the cart. I have the Woocommerce Cart widget in the side bar of my shop page showing the cart present content, and the theme I'm using (WooThemes PixelPress) is also showing the number of items in the cart in the top menu bar on every page. When I start by clearing the W3TC caches, and go to the shop pages and add a product to the cart, the cart and the menu bar widget is updated correctly in the shop page. However when I go to the main landing page after adding the item, the cart shows 0 items, but if I go to Blog page for example the cart shows 1 item. I take this is because after clearing the W3TC caches I first visit the landing page which is cached by W3TC with the present cart state (0), but I never go to Blog page until after cart update, which is cached after adding the item. Also when I go to cart page, remove the item and go to shop page it still shows that I got an item in the cart in both the cart widget and the menu bar. So it seems that W3TC caches the pages with the cart status that was there when first visiting the pages for the first time. Worse, this seems to spill over to other people visiting the site so that if I add an item to the cart which is then cached by W3TC, it shows this cart state for someone else!
If I disable W3TC page caching (thus all caching) in W3TC and repeat the test, the problem goes away, but obviously I would like to have caching enabled for performance reasons. I also noticed there's option in Performance => Page Cache general settings called "Don't cache pages for logged in users", which I assume I could use if I would expect people registering and logging in to the site before doing any shopping, but I would rather not do that because it adds annoying step for customers before they can do shopping, thus probably shows in conversion rate (I personally hate that kind of stuff).
So do you have any suggestions how to fix this issue? I probably just have something incorrectly configured but after several hours Googling for it and trying different things in W3TC settings I haven't been able to figure out how to properly fix it. I'm not 100% sure either if this is really a W3TC issue, WooCommerce issue, an issue with the PixelPress theme I'm using, or some mix of the three.