Supagard is semi decent if you put it on yourself. However, having said that beading doesn't necessarily imply protection. Sealants such as Supagard tend to sheet more and have irregular beads so thats not really the best way to test protection.
The problem with the dealers is they rushed it (110% sure about that) therefore you'll not only find swirls in the sun but it won't last anywhere near as long as it should do.
It costs like £30, no doubt some will pay £200 for it but its simply not worth it. Its a sealant, you can stick wax on it if you want. If you polish it, it'll remove the supagard but then, it doesn't last more than a month or two anyway due to dealer application.
Aqua wax won't remove it and neither will Autoglym wax - the SRP will though.