The trick with the + suffix is very old, I think it might be a unix thing. It's neat to see it work in Gmail.
Official Gmail Blog: 2 hidden ways to get more from your Gmail address:
...Append a plus (' ') sign and any combination of words or numbers after your email address. For example, if your name was firstname.lastname@example.org, you could send mail to hikingfan email@example.com or hikingfan firstname.lastname@example.org.
Insert one or several dots ('.') anywhere in your email address. Gmail doesn't recognize periods as characters in addresses -- we just ignore them. For example, you could tell people your address was email@example.com, firstname.lastname@example.org or email@example.com. (We understand that there has been some confusion about this in the past, but to settle it once and for all, you can indeed receive mail at all the variations with dots.)...
Personally, I prefer to use disposable Bloglines email addresses for the sorts of things the + suffixes are used for.