Number free permalink structure advice

I’m a Drupal refugee, new to WordPress, but with a good bit of cms & php experience. I’m struggling with permalink structures.

For most of my sites the date of publication is not terribly relevant. The post ID is clearly irrelevant. However I’ve read a good deal about the importance of starting post permalinks with numeric data. In addition to wanting to keep numbers out of my URLs I’d like to keep dead segments out of the URL, by which I mean if Uncategorized shows up at /category/uncategorized then something other than 404 better show up at /category. Given these requirements what would experienced WordPress users suggest for permalink structure?

I’ve come up with the following options:

• Use the no category-base plugin and set permalinks to /%category%/%postname% so a category archive shows up at /uncategorized and a post shows up at /uncategorized/hello-world. The problem here is that I’m not wild about having categories be top level URL segments and obviously I’ve got to be careful about naming conflicts.
• Set permalinks to /post/%postname and leave category URLs unmodified. The problem here is that /post ends up being required in unexpected places like /post/2009 (expectedness debatable) to get the year archive or /post/series to get at post series made by the Organize Series plugin.
• Set permalinks to /%postname and leave category URLs unmodified. This seems to work but has huge name conflict potential and posts clearly should not be top level URL segments.
• Set permalinks to /%postname.html and leave category URLs unmodified. This actually seems to avoid most of the URL collisions but does require posts be top level items.

At present I’m leaning towards the last option. I’ve built a few test sites and done a bit of performance testing and with minimal caching and optimization efforts performance does not seem to suffer compared to permalinks starting with a number. Then again I’m only testing with 200 posts and 600 comments in my database.

As for dead segments I assume this is just a matter of not finding the right section in the theming documentation. Can someone point me towards how I can put an index page at /tags and /categories? I’ve worked out the php and theme tags to make the html I want just, but not how to get a page to respond to those urls.

Thanks in advance for all the help.