I've purposely been avoiding this thread, because I'm sure people are tired of hearing my opinion of hydrometers.
They do obviously have value. To an AG brewer, I can see them as being much more important. And if you want to KNOW (not estimate) your abv, then they are almost necessary.
But, just cruise the forums and look for posts from extract brewers who are worried about their batches because the SG was off or the FG is too low/high. I bet that 99 times out of 100, there is no problem. The yeast just attenuated a little out of range or they added too much/little top-off water, or they took a misrepresentative sample for SG, or they are using the thing improperly, or.... whatever. I don't think the device is worth all the fuss.
When I started brewing, I checked gravity. I checked it a lot. I checked at the start, I checked before racking, I checked for "3 static readings" before bottling, I checked on Tuesdays, etc. What did this get me? A few broken hydrometers, a lot of numbers, contamination risks, and ABV info that I never really cared about, but found novel.
The novelty eventually wore off.
I switched to only using it on BIG beers (SG > 1.070). I broke my last hydrometer when I brewed my espresso stout in October and swore I'd never buy another one. But, then I bought a wine kit that required rackings and additives at certain gravities, so I had to buy another one.
I might (read: probably) have batches where my ferment stops shy of an estimated 'proper' finishing point... but.... ummm... who cares? Like cheesefood said; Never Look Back. I've got one for my wine, but I won't use it for my beer.
-walker