The Indian Regional Navigation Satellite System (IRNSS) has recently (May 2016) become fully-operational. In this contribution, for the fully-operational IRNSS as a standalone system and also in combination with GPS, we provide a first assessment of L5 integer ambiguity resolution and positioning performance. While our empirical analyses are based on the data collected by two JAVAD receivers at Curtin University, Perth, Australia, our formal analyses are carried out for various onshore locations within the IRNSS service area. We study the noise characteristics (carrier-tonoise density, measurement precision, time-correlation), the integer ambiguity resolution performance (success rates and ambiguity dilution of precision (ADOP)), and the positioning performance (ambiguity float and ambiguity fixed). The results show that our empirical outcomes are consistent with their formal counterparts and that the GPS L5-data have a lower noise level than that of IRNSS L5-data, particularly in case of the code data. The underlying model in our assessments varies from standalone IRNSS (L5) to IRNSS+GPS (L5), from unconstrained to height-constrained and from kinematic to static. Significant improvement of ambiguity resolution and positioning performance are achievable upon integrating L5-data of IRNSS with GPS.