Well that's a nifty little feature, the bulk majority of simple micro's don't have it though.
I agree. I'm new to PIC's, I'm more trying to understand whats going on under the hood than save a buck. The only reason I was considering the internal osc. was to eliminate three components and simplify the design, not for the cost of the parts.Hmm, hes using; "18F4620., cellular modem at 9600, LCD display and communication to a RTC via I2C." all of that sounds farily expensive. Just add a $1 xtal to drive the PIC at a stable baudrate.
It would be sheer lunacy to pay for all of those peripherals and then try to save the cost of an xtal and use the internal osc for something that needs reliable comms at a "temperature range of -30 to +60C.".