To express the idea of "Honestly, some people!" (said irritatedly), in conversation I said jokingly:

Tu ne sais pas que c’est mal élevé d’interrompre une conversation ? Franchement, il y a de ces gens !

I wonder though if this phrasing gets across the meaning well enough, or for that matter, if it is commonly used.

While the translation of "some people ... (others)" is as straightforward as they come, when it comes to this specific usage, there's more to it than meets the eye.

In German and Spanish, for instance, idiomatic phrasings for this are "Also wirklich, Leute gibt’s!" and "¡Desde luego, qué gente!" -- in a similar vein, to be sure, but with a slightly different flavour.