We have a lot of reports in the past few weeks of messages from us not getting to people's Gmail inbox but getting marked as Spam and ending up in the Spam folder (we've had that happen with a couple of vendors as well as a lot of customer). Also, with the new Tabs feature for your Gmail inbox may put them in one of the tabs other than Primary. So you should check those tabs if you have converted your inbox to use them. If you move a message to a particular tab Gmail seems to learn that's where you want it to go.
We assume Google has tightened their Spam filtering and it's catching a lot of things that are not Spam from legitimate sources. We recommend you check your Spam folder once a week and mark which messages are not Spam. Hopefully Gmail will learn.
For our newsletters we post those to the website within a few days of them being sent out. If you have placed an order with us either online or via e-mail and are not hearing back from us, do check your Spam folder, regardless of who your e-mail provider is. In the past week alone we've had more than a dozen people find our messages regarding their order, in their Spam folder. Best to check it on a regular basis.