If you doing anything with precision timing, the internal oscillator has 2/3 % error at 7.323MHz. I use a SMT xtal with the caps. An external supervisor is recommended since the 936 as mentioned sometimes comes up funky. Personally, I like ICP over ISP, but ICP kills the bootloader, but using flashmagic, it doesn't really care since there is bridge code and gives all the same options as ISP as far as flashmagic is concerned.

The Keil reference circuit works if you build it exactly as they show it and don't add "your own thoughts" to it. I use both ISP and ICP so six in one/half dozen in the other.

Regards,