but to me, having just one person paying for and maintaining a virtual server + the vBulletin software is an unacceptable risk. What happens when Andrew decides not to pay anymore after 12 months. What happens when the server locks up and needs rebooting? What happens when updates need to be installed? What if the mailing from the server stops working? Is there a failover mechansism? Is there a business continuity plan? I have maintained servers myself and I can tell you: they will fail once in a while.
The risk in using Google Groups is very low, as it is maintained by Google and runs thousands of groups, some having a massive number of active members. It is free and ownership and administration can be shared or transferred.
In terms of use, I believe Google Groups has sufficient features. There are mainly 2 ways how people use a forum:
1. Find answers: you need good search capabilities. The advanced search capabilities are similar to vBulletin
2. Learn: reading all new posts. Marking read posts, e-mailing daily digest is similar to vBulletin
The main difference is the looks. Google Groups is simple. We even tried to make it even more simple by not setting up the sub-forums / categories i.e. not copying the structure of the original forum because everything posted in a single group is easier to read new posts (Learn), and you do not need the structure to find answers. Just good search capabilities and tagging.
I don't think we will get the German speaking community on the same page and have everyone post in English only. The German speaking community is just too big. But we might be able to convert some of them in the future if we get a single large active forum in English only.