It heats a bit after a few hours of intense usage, but it is stable after that. The external plastic seems durable to cope with those temperatures (<50C from my experience). Usb and micro sd also suffer from heat when in usage with smb, but I have seen far worse (micro sd should handle <=80C well, usb similar).
Until now I have not seen the fan active, despite forcing the system with 10 devices with video and smb usage. So I think it is disabled by software for now (or there are sensors and enabled only for t>t_0, t_0>50C).
Repositories are still incomplete (cannot install transmission yet), so perhaps there is a lm-sensors package in the future.