I've done one on my LMS Mini-mill. It's ALL about workholding.The big problem you'll run into is the tooling length to cut the deep pocket, but if you know what you're doing, it's not too bad. Certainly doable, but it's about at the limit of my little machine's capabilities, in terms of rigidity - getting a good surface finish (so it looks pretty) takes some concentration.
ETA: What sweptvolume said about the table is very true. Hobby mills are good to start out on if you have some basic skills, and want to hone them. If you start off with some simple projects using soft materials and work your way up, they can be great to learn on. The big problem is that you have to work harder to get pieces mounted well, and to keep the machine true. On a bigger machine, you can focus on other parts of the process, but if you're doing anything of appreciable size on a mini-mill, your setup has to be good. Good machinists can do some amazing things with these small mills (I know of a guy using one to make some VERY nice mechanical watches - gears and all), but it takes a lot of practice and experience to get to that level. An 80% lower is a good intermediate project, but I wouldn't start with it, and I would say there are plenty of other things that you will eventually consider to be 'beyond' the skill level that was necessary to complete it. Its size is the limiting factor - not its complexity.