While most particle physics models from string theory have been constructed in settings with some amount of supersymmetry, there has not been any experimental evidence, that it is actually realized in nature. We show that by starting from non-supersymmetric heterotic strings it is possible to construct models which have particle spectra surprisingly close to that of the Standard Model of particle physics. However, all these models seem to suffer from at least two caveats: The spectrum contains a large number of additional states, which do not have clear physical interpretation. A huge cosmological constant seems to be always generated at the one-loop level in conflict with the observed experimental value and leading to various stability issues.