...you spend 30 minutes deleting 100's of effects and sends from a project you've been tinkering with for months, hit play, and realize that it sounds 1000% better. 

 Been there (a few times)...

If I get a mix from someone that was done in Sonar and the fx are all still available it's oh so interesting to bypass all the fx. It often sounds so much better. Just because you have 1000 plugins doesn't mean you have to use them. Sometimes what you recorded is the right sound, and after all, isn't that the general aim.

When I'm mixing tracks I've tracked, I always start with unprocessed tracks and see how far I can go.

It's become part of my process.
 
The mix isn't done until I've gone back and removed or bypassed every plugin to determine which ones were helping and which ones were not. It's rare that I don't exorcise at least one plugin in the process.
 
The most common type of processor to get the boot: harmonic exciters and distortion. They tend to sound neat when you first stick 'em in, but the cumulative effect of multiple harmonic distortion stages can result in a harsh-sounding mix. 

Hi,
 
That is the main reason why I usually only do it "once", and only clean up the English after ... that little moment does not exactly repeat itself ... and adding anything to it, changes it. It's the same thing with improvisations, except that most people think that they are not worthwhile as music, and that you can only take bits and pieces from it. 
 
but there are times when it works ... and you will also surprise yourself!

bitflipper
It's become part of my process.
 
The mix isn't done until I've gone back and removed or bypassed every plugin to determine which ones were helping and which ones were not. It's rare that I don't exorcise at least one plugin in the process.
 
The most common type of processor to get the boot: harmonic exciters and distortion. They tend to sound neat when you first stick 'em in, but the cumulative effect of multiple harmonic distortion stages can result in a harsh-sounding mix. 

 
Yeah I've noticed that. Distortion really does sound harsh when it builds up over multiple tracks, especially if you've been sticking the same distortion plugin on all of them. It can reduce clarity as well. Sometimes I find that if I turn off all of the console emulators I have turned on, or at least turn the drive knobs down on most of the tracks, I get a nicer sound. 
 
EQ is another one that gets too overdone. It's so easy to go nuts with complicated EQ curves that you've worked out in a theoretical manner, i.e. lots of "complimentary" cuts and boosts with the idea that you're creating some perfectly interlocking mesh of frequency jigsaw pieces. Before you know it, your 4 bands aren't enough and you're throwing multiple EQ's on each track just to accommodate all of the boosts and cuts, and not only have you thrown away lots of perfectly good frequencies but everything's starting to sound a little phasey from all the filters. It's very easy to go overboard with high pass filtering as well, sometimes filtering not only the individual tracks but then the various buses they're fed to. You end up filtering tracks that have already been filtered and just suck all of the warmth out of your music. But hey, there's this HUGE space for the bass and kick!