Well, the first thing I realized is that although the cloudkey is cool, if you don't care about stats, you are better off just firing up the PC app whenever you need to make changes. It is cheaper. If you think the stats are something you would like to look at once in a while, then yeah the cloud key is awesome. It is definitely something you can grab later, as it is not necessary.
Second thing, the US-8-60W gets pretty warm, so leave it in an area where it gets good ventilation.
The USG is in a weird spot right now, it is essentially a product that is designed to be able to do everything in a really slick clean UI. For the most part you can do that, and it is really easy and almost Apple like. On the other hand, quite a few features are actually harder to implement on the USG as compared to the ERL, because they haven't added them to the UI yet. Things like IPv6, UPNP (which I wouldnt use anwyay for security reasons), Radius server, and IPSEC/L2TP are all coming in the near future (next few months). Right now though those things can only be implemented by SSH into the router, editing the CLI, exporting a config and re uploading it as a json....so yeah if you want those things you had better be able to read forum posts and figure it out. Other than that though 99% of what a home user wants to do is super simple. VLANs, port forwarding, dynamic DNS, DPI etc.. all easy.
Personally, I would piece meal everything and add stuff as you need it. Get the switch first, because you need it. Later, grab a UAP AC Pro, add it as an AP to your R700, maybe later grab the router to your replace the R700, and finally a cloud key. That way you aren't forking out a ton of money right off the bat. All the cool stuff wont be available until it is all together, but individual pieces will work before then.
