  Synoptic spectroscopic observations of the U Sco 2010 outburst from maximum
light to quiescence as well as a contemporaneous X-ray observation are
presented and analyzed. The X-ray spectrum 52 days after outburst indicates a
hot source (kTbb ~ 70 eV). . Narrow line components from the irradiated
companion atmosphere were observed in hydrogen and helium optical recombination
lines. The formation of a nebular spectrum is seen for the first time in this
class of recurrent novae, allowing a detailed study of the ejecta using
photoionization models. Unusual [OIII] auroral-to-nebular line ratios were
found and possible scenarios of their origin are discussed. The modeling of the
emission line spectrum suggests a highly heterogeneous ejecta with mass around
or above 3 x 10-6 Msun
