I recently learned that the strength of a Magnetic field around a conductor is proportional to the current flowing in it. So if we have a Mercury wire at absolute zero and pass a current through it (Resistance = 0) and then toss some iron filings at it, will the filings cylindrically float around the conductor (along the Magnetic field lines) due to the extreme strength of the field or just behave the way they do for an ordinary conductor (like Copper), in which case we must rest the filings on cardboard and then give it a jerk to align it along the lines.
First thing: even with huge fields, iron will not "float" like that in circular motion. Iron will always be attracted to the region where the magnetic field is the most intense: which is in contact with the conductor/superconductor.
In addition, there is a limit to the magnetic field you can achieve with any superconductor: it is called the critical field. There are 2 types of critical fields, Hc_1 and Hc_2, which correspond to 2 things:
The "floating" of magnets above superconductors, are due to these vortices, which cannot move in space as freely as usual magnetic flux lines in vaccuum can. This phenomenon "traps" the field exactly as it is, and the magnet with it, and only a force above a certain threshold (usually higher than the weight of the magnet used for the demonstration) can move the magnetic flux lines inside the superconductor.
This "floating" is the only difference in principle between superconductors and usual conductors.
One last thing: you can have objects, even living creatures like frogs, floating inside a copper coil, but this happens only with very high fields (more than 10 Teslas for water, see http://en.wikipedia.org/wiki/Magnetic_levitation#Diamagnetism)
Hope I answered your question :-)