Just to name a few:

1)
DIV AB works incorrectly when the preceding instruction is MOV A,smth. So:

mov B,#1
mov A,#2
div AB

works incorrectly

mov A,#2
mov B,#1
div AB

works OK!

2)
UART0 or 1 can receive ghost characters when working in MODE 3 with multiprocessor feature enabled and previous RB8 was set and there wasn't a match with character/address masks. This
is official version of the bug. In my revision (B2) UART mode 3 doesn't work correctly at all, depending on baud rate and instructions layout (sic!)

As for 8051 compatible uP this is quite a funny situation, isn't it ?

Mark