The diffraction limit in optics corresponds to the Heisenberg uncertainty limit for atoms. In an ideal case, the atom laser emits a Heisenberg uncertainty limited beam. Photons can be created, but not atoms. The number of atoms in an atom laser is not amplified. What is amplified is the number of atoms in the ground state, while the number of atoms in other states decreases.
Atoms interact with each other - that creates additional spreading of the output beam.
Unlike light, a matter wave cannot travel far through air. Atoms are massive particles. They are therefore accelerated by gravity. A matter wave beam will fall like a beam of ordinary atoms. A Bose condensed system is in thermal equilibrium and characterized by extremely low temperature.