Vivado is required for all advanced features and programming Xilinx chips in general; like the sibling post said, there is no open FPGA toolchain implementation for Xilinx devices, especially for extremely high end ones like the ones being offered on the F1 (I expect they'd run at like, several thousand USD per device, on top of a several thousand dollar Vivado license for all the features).

It doesn't look like there's much AWS proprietary stuff here, though we'd have to wait for the SDK to be opened properly to be sure. I imagine it's mostly just making all of the stuff prepackaged and easily consumable for usage, and maybe some extra IP Cores or something for common stuff, and lots of examples. If you're already using Vivado I imagine using the F1/Cloud won't introduce any kind of major changes to what you expect.