I don't write a ton of nodejs modules. I work on a few*, and I don't even work on them as much as I like. However I do end up using a ton of them. Here are some cool things I'd like to see that would make my life easier as a node developer.
We see the latest readme, and the latest version number, but no info on the old versions. You'd have to go download them and check their readme's and and docs.
More support for docs
The readme is awesome but I'd love to be able to link to a doc site. The `man` option is cool but widely unused. Web docs may vary widely in quality and scope but they're googleable and have become a staple.
The 'directories.doc' directive mentions linking to a markdown formatted file that might get displayed in the future. That is also not widely used but would be a step in the right direction.
Finally I'd like to have versioned docs, I'd like to be able to see the readme and docs for a package at any point in it's life. Often I find a lot of modules in use that are out of date and even if there are good tests which might make upgrading easier, upgrading a module so the docs are relevant is silly.
That's it for now. It's not a lot to wish for. NPM is in great shape and I'm quite happy with it. =)