I've just ordered a couple of Ubiquity and WRT54GL devices to start playing around. Keen to get started.

While searching about hsmm-mesh online I've come across other mesh technologies, such as qmp, batman, cjdns, etc.

QMP for example is what's used in Guifi.net.  QMP is not an amateur specific technology, but it's been rolled out in Spain for thousands of nodes. They might be running low EIRP - but the network can support a LOT of nodes and traffic.

In comparison - would hsmm-mesh be up to the challenge if we were to run hundreds of nodes together?

I'm keen to learn how the 2 technologies compare.

For starters I'm working on an AREC (aka ARES in New Zealand) solution where it wouldnt really matter - but as time goes on and more networks were linked (say even over VPN to the US or otherplace) I'd like to learn if there will be any bottlenecks.

Thanks.

Your question came in on a release week, this means most the people whom might have the skill to answer this question are generally fairly busy.

All mesh technologies have the same need,  they need to publish the details of nodes in a network so that way a routing decision can be made.

Scaling depends on a LOT Of factors, everything from number of nodes, to distance between nodes, link quality between nodes, settings used for propagating the information.

It is impossible to give a exact scaling factor for any network.

Most routing projects share one of a few common daemons, OLSRD and Batman are the two most common to my knowledge  with OLSRD  being a defined standard.

QMP is actually just a frontend of some solution I have never heard of,  and the CJDNS you linked talks about being an encrypted protocol which may not work for Amateur Radio.

Like most items in networking one has to evaluate the deployment and watch how it is performing and evaluate changes in response to the needs of an environment.