Google Drive ~Never used.
Google Music ~ Never used.
YouTube ~ Metrotube does a fantastic job.
Google Maps ~ I'm not sure if I ever used Google Maps, to be honest, seeing as my first smartphone was a Lumia 900.
Gmail ~ I've fallen in love with Outlook, especially the alias feature. I'm slowly but surely transferring all my online accounts to recognize Outlook as my email address, not Gmail.
Overall, don't miss Google at all. Granted, I hadn't invested myself in any ecosystem before I got my first smartphone, the Lumia 900. I kinda got invested in Apple's with my iPad, but that only apps. I did pick up a Gmail when all the kids said it was all the rage, it critiqued me for using Yahoo (I'm 15, if anyone's curious). Thus, I made it my main email and I've been using it for years, so getting every account to recognize my Outlook will be a chore, to say the least.
It basically seems that I'm siding with Microsoft in the ecosystem wars, and I must say, it's a nice one at that. It still has its kinks, such as Windows 8 and Windows Phone 8 utilizing different app stores, and integration between all of Microsoft's products and services needs more development (I.E: my color theme being able to follow me from device to device, whether it be a Windows Phone, a Surface Tablet, an Xbox or laptop, I want all my customization and setting to follow me via the cloud). But Microsoft's offering is very robust and done well, and its increasing presence in Microsoft products makes it a great place to be if you're a Windows user.