hi,
well, I have not used RD2 but I know that most Atmel products come out as bug-free but then, after some months, we are surprised with fresh Erratas.
BTW, it is AT89C51RD2 which has 2 pages Errata; T89C51RD2 has it on 6 pages!
As already was said here, it seems that Atmel uses their users as testers :(

Now I cannot imagine which surprises I give at time when our board and software will be prepared.

Regards,
Oleg