For it's i-part, i-Installer relies heavily on access to http (ftp, not working properly, not even in Mac OS X 10.3.2) servers for i-Directories, and updates/downloads from i-Packages. These servers may be busy, down or even may have disappeared. This might influence i-Installers capabilities as well as its performance, the latter mainly because you end up with network time outs that may last up to minutes, and who is patient enough for that these days?
One option is to open a package from a remote URL and make it fat (download everything) and then lock the package. But you will lose the dynamic part of i-Installer if you do this. Another way to improve network performance is to set up a local mirror.
If you want to make sure i-Packages are available on your local network (say a campus network) without i-Installer users having to try to download stuff every time from remote (possibly slow) locations, you can set up a local mirror easily enough. Just mirror the i-packages directory on one of the existing web servers. When you have a local mirror, you can open the packages through local URL's and i-Installer will use that URL for checks, downloads, etc. It becomes your responsibility of course to keep such a mirror up-to-date. Note that currently only http access works well from within i-Installer, so while you can use ftp, rsync or whatever to maintain your mirrors, you need them to be available through http for i-Installer to be able to use them.
You can open those locally mirrored packages through the New from URL... menu item, but you'd rather use the known packages window. To do that, you must create an i-Directory. The easiest way to do that is to make a copy of one of the existing i-Directories (e.g. i-packages/iid/gwrelative.iid) in another name (e.g. foo.iid) and edit that one. Change all package URLs mentioned in foo.iid to your local mirror and use relastive URLs so that you can easily move the whole setup. Do not edit the packages themselves, that will break them.
If you set the URL of that new i-Directory in your preferences, you will get the new entries in the Known Packages window. If you set the descend level to 1 (one directory) you will get only what is on your own i-Directory.
If your mirror is also available to the rest of the world, send the i-Directory URL to email@example.com so it can be added to the web of i-Directories.