The Positive Side of Negative Keywords, Part 2 - Negative Match Types

Last week, I posted this introduction to using negative keywords to get better traffic and save money.

Now, I want to talk about (and get opinions on) another part of negative keywords that many Adwords advertisers may not be aware of - negative match types.  Here's what they look like:
Broad negative (default): -memory cards
Phrase negative: -"memory cards"
Exact negative: -[memory cards]

I wanted to talk about these here, because Google doesn't even go into much about these.  After much searching, I found this post on the Inside Adwords blog from November 2007.  It actually provides a pretty decent chart that explains the different negative match types.

This is really good information to have, as I found out managing a rather large Adwords account.  I had all broad negatives; but upon generating and checking several search query reports, I found that my ads were still being served on keywords I thought I'd eliminated with negatives. 

I eventually brought my costs down by changing all of my negatives to negative phrase match; but who know how many hundreds of dollars I wasted on those keywords!  It's really too bad that Google kind of hides it away, as many new, less experienced advertisers don't have that much of a budget to just throw away.

I'd like to get others opinions - how long were you managing Adwords campaigns before you found out about negative match types?  Once you started using them, did you see a significant difference?