Like many others, I'm anxiously awaiting arrival of my 16gig Nexus 7 tablet. I have an Acer Iconia Tab A500 that I bought year ago. When I bought it I was thinking strongly about getting the 7" Galaxy Tab strictly based on the size, as I wasn't sure I wanted a 10.1" tablet. I've enjoyed the A500, and have gotten a lot of use from the full size USB port. (You should have seen the looks of envy I received from a room full of iPad users at a conference last month where they provided all attendees with a USB thumb drive with conference materials on it. I popped it in my tablet and several were saying, "Is that an iPad? How are you able to use that drive?")
I admit I fall into the camp that would prefer at least micro SD capability with the Nexus 7 (I have a 32gig card in my A500), but realistically I can have all I use on a regular basis well within the capacity of the 16gig Nexus 7. I plan on keeping the A500, but anticipate using the new Nexus 7 most of the time.
My current usage of the tablet primarily is for Bible study/teaching, personal finances, email (personal and work), Facebook, and internet browsing. I also use Pandora quite a bit.