When we first started the forum up we umm’d and aaahh’d about if to show the ‘Latest’ view (which shows the recent posts by activity) or the ‘Categories’ view (which is more like a traditional forum, where categories are like ‘sub-forums’) when people visit forums.mudspike.com.
We did polls, we threw tea-leaves, we changed it a bit randomly.
Finally, because I am inherently selfish, 
I set it to what was most useful to me. The ‘Latest’ view is good if you already know the categories we have here, but sort of sucks for new users. My attitude at the time was ‘I don’t know these people, I’m sure they will be fine’.
Anyhoo, we now have a way for each of you to set your own user preference.
Click on your Avatar (top right) → Click on the cog icon 
-> In the list on the left click ‘Interface’
In that list of options you’ll see this:
If you are a forum old hand then you’ll probably want it on ‘Latest’. The new default has been set to ‘Categories’ (which does have a mini activity stream as well) to be easier for new people to get their heads around.
Let us know if this causes any angst.