I use the SiLabs parts too, mostly the 'F320 and 'F340 series in USB based bus powered devices. Very low parts count with the built-in oscillator and 3.3V regulator from VBUS. I like the mix of I2C, SPI and dual UARTS.

But all thing must pass. I'm not likely to be using 8051's much in the future. The small Cortex M3 and M0 ARMs are looking better every day. If one of the ARM parts ever gets to the same level of integration as the 'F340 I don;t see much future in new 8051 based designs.
Jack Peacock