I've been fixing up old button/script posts from before we changed forum software, and noticed that this one could be sped up when calculating more than one hash type.
The DOpus.FSUtil.Hash method lets you specify multiple hash types so they can all be calculated at once. (We may have added this to Opus after this script was written. I'm not sure.) That can make it a lot faster with large files, since they only need to be read from disk once.
An example of how it works can be found in my post here in this thread Button: Show MD5/SHA (which is about some buttons that do similar things).