The categories are very reasonable, and its a short list - which is a good thing. We might want to roll “Site Feedback” into “Uncategorized”, as it will likely not be used much. It will probably be used somewhat in the first few weeks, so we might want to wait a little bit with merging - assuming merging categories is easy.
Users and developers will not be separated, aside from separation created by visitors themselves by setting up filters and subscribing to some categories but not others.
It is a good question whether “Community” is for user questions. Perhaps we should have a category with a name suggestive of that? And make that category be the default? Most visitors will want to ask a question about using ITK, much less people about developing it.
Anyone who uses ITK is a developer that is developing it. The “lesser” attribution to new developers as “users” does not encourage contribution from folks who have a lot to add to the community.
To encourage new participation, maybe a “Beginner” or “First-Timer” category?
“Beginner questions” sounds good. Most people will want to start by posting in that category, unless they are able to categorize their post which means they are not beginners
“Beginner questions” sounds good. Most people will want to start by posting in that category, unless they are able to categorize their post which means they are not beginners 
Can we make beginner questions be second category right after announcements? Can beginner questions be made the default category for new topics? If not, can it be second on that list, right after “Uncategorized”?