I don't know what you have inside your folder, but I only have NAV items inside mine. If you have NAV, I'd keep those items, and any others that are needed for critical applications. If there are items for software that you have already removed, then I would say it's safe to remove them.
Probably the safest way to do that would be to use the system preferences. If you go to 'login', there's a list of the non-essential programs that start-up when you login. Just remove the one's you don't want in there.
the startup items in the "login" preferences are for programs that start on login to the computer...items in your startup folder int he library start up when the computer is turned on for appz like SETI@HOME...therefore, it is ok to delete items from this folder as long as you aren't planning on running the programs listed in there...eg. To run SETI when you login, when the computer is staring up, in the progress it will say "starting seti screensaver" or something. If it doesn't do this, you won't be able to run SETI when you login, hence the need for a restart after installing the SETI package