I looked at the topic and post counts for Joomla 1.0 and 1.5 in two forums, the one where end users ask general help questions, and the one where developers have specific code questions. The results shown in the graph below I thought were *really* interesting.
To me, this really shows the trend. Many many end users are still working on 1.0, but clearly, there is a huge amount of developer activity on 1.5. I interpret this as meaning 1.0 might still be the Joomla version of right now, but 1.5 will be the version of tomorrow.
Now, the graph shows total numbers, and obviously 1.0 has been around for a long time. A much better comparison would be the same data for say, 2008 only. Maybe a Forum Admin might provide that ;).
One other bit of data that is more timely is the number of downloads from joomlacode.org. Looking at the most recent builds of both versions:
Here 1.0.15 has the slight edge, but again, I thin kit has been available longer.
Anyway, the answer I have prepared for this question?
"If you are building a new site and don’t have many extensions, make sure it will be future proof and use Joomla 1.5."
What do you think?