Personally I prefer the Flycam styles, but the Nano is pushing it with a full DSLR setup on top, which is why they do a whole series (the 3000 is a better choice for the weight of a DSLR with pro glass, it'll even cope with rails and a FF).
One advantage of a vertical stick is that you can put stuff on the bottom sled, such as a battery pack and monitor (the more you put on the bottom the more you can then put on top). If weight becomes a pain - and it will - then you can always add an arm brace and vest.
As to the 'not using it much' - I think a lot of people new to DSLR video are tempted by the blog chatter about these things, but look at the motion picture sector in comparison. We fly things, but it's very much a last resort because it creates far more problems than it solves - sliders, dollies and cranes all come first. Flying only makes sense if the camera is tracking a fixed horizon at a fixed distance - you can pan with some care but you cannot tilt at all. You have no access to the camera controls, you can't zoom or pull focus without an electronic FF and balanced lens. You can't even look through a loupe, so outdoors you'll want an external monitor.
If you're standing still, you're always better off with a tripod or monopod. In a studio a dolly cart or crane are more flexible - I know cranes are expensive but given a decent floor you can dolly off anything with wheels (a DIY dolly cart is insanely simple compared to a DIY flyer). Flying works as a follow shot if the camera has to walk through a street or around a building and you can't use a cart for space reasons, but try walking around with your eyes fixed level; it's a strange viewpoint on the world so it only works for short cuts. Doesn't matter if you're using a Flycam or Steadicam, it always takes a while to balance these things so if time is an issue (e.g. event shooting) you may miss your only chance to capture the action unless you have multiple cameras in play.
Flyers have their uses; if you're filming interiors for real estate commercials it's going to be easier to get one through the doors, but buying one won't make your footage any better - just different - and it'll take a while to become proficient.