We use Portmaster 3's here in Europe on ISDN PRI's
with great success. K56Flex nearly never connects under
40k here. The product runs very stable. Never had a crash
or reboot of the PM3. For the rest we are very satisfied with
the PM3 and its features now that COMOS 3.8 stands before
the door. We also used PM2 before which were nearly perfect
products for analog dial-ups.
In my opinion CISCO also offers a very good RAS with the
AS5300 however it costs a lot more, not forgetting the software
upgrades.