Vista - Load balancing solution

We are having a .NET website where we would like to have load balancing.
There will be two front end web servers (iis), serving traffic coming from an
Akamai layer (which will replace the client ip address in the request with
the one from Akamai). Because of this Akamai layer, we will have to use a
load balancing solutions other than NLB Manager from W2k3, but rather a
solution which does the affinity / persistence handling based on cookies or
similar rather than looking at the IP address.

Another solution would be to use an out-of-proc state server solution, but I
would like to avoid this in order to not have an additional server round trip
(performance lost?) and for minimizing complexity (additional db server,
potential serialization issues).

Could you suggest any state of the art solutions (hardware or software
based)? What are you using?

We expect 2000 concurrent users at peak times.

Thanks,
Juerg