Loadbalance outgoing traffic over two cable modems in same network

[Mel Flynn]

Hi,

I've looked over http://www.openbsd.org/faq/pf/pools.html but this assumes two 
different gateways for the two interfaces.
I'm faced with two cable modems from the same ISP, with the same gateway. I 
can't lagg(4) the interfaces, since specific IP's are bound to specific 
modems.

So I'm wondering if using stick-address with a round-robin nat pool is really 
sufficient to do load balancing of outgoing traffic and not get into session 
problems with various protocols. Has anybody had similar experiences?
-- 
Mel