The Baggs M1 set a new standard for useful and natural acoustic tone in a magnetic soundhole pickup. It did this by combining the stringy immediacy of a traditional magnetic pickup with a top-sensing floating humbucker. Of course, it's not as natural as a microphone or soundboard pickup, but to this day the M1 comes about as close as any soundhole pickup to keeping your acoustic from sounding like a Strat.
The Baggs M80 takes this one step further: By allowing the floating humbucker to float more freely (Baggs has changed how the second pickup is suspended), the M80 captures even more of the motion of your guitar's body. All this adds up to an even more acoustic tone. They've also loaded it with some welcome new features, including a battery indicator light (why doesn't every active system have one of these?) and an active/passive switch, so it's kind of like getting an M1and an M1 Active in the same package.
If you've been in the market for a soundhole pickup, but have been wary of the electric nature of the tone, I think the M80 is a great way to go.