I see no real need for any sort of OS in an embedded environment, since the tasks are all well defined, the sequence of them is well defined, and they're small. If your application is too big for your MCU, you don't need an OS to fix it, you need a bigger MCU. Not everyone sees things this way, but it's likely to remain that way despite my beliefs or anyone else's.
I a way I agree, and with the '51 I do so fully. However e.g. a cellphone is "an embedded environment" as well and i doubt I would approach such a task without an OS.

this article http://www.embedded.com//showArti...=196800005 , which everybody should read, basically makes the point "use 'small' architectures withouth a RTOS e.g. in the section: To determine the best CPU for the application, example pieces of code were compiled using the best compilers I could find for each CPU candidate and the energy consumed by each CPU calculated. The results were quite clear: the older CPUs such as the 8051 and the HC08 had a distinct advantage over the newer, register-rich architectures. This advantage was due in part to the low ISR overhead of these devices. In the case of the 8051, this advantage also had a lot to do with the fact that the 8051 allows one to allocate a register bank to a particular block of code--such as an ISR--and thus drastically reduce the number of registers that need to be stacked.

BTW, Richard, I found out what your problem is :) I read in Embedded System Design (if you do not get it, subscribe) the following: "Experiments in 1984 showed that memory devices has twice as many soft errors in Denver than at sea level" ESD January 2007 pg 54.

Erik