Tape emulation in a digital realm is a very interesting subject to study. Please, share your thoughts on
1. How
2. When
3. Why
you use it, and
4. What is your favorite Tape Emulation plugin?

I use tape emulation plugins on every track. I treat my signal flow like it's coming from multi-track > board inputs so the tape emulation is first for me.
Used to use ProChannel's tape emulation module but when I tried Slate's, boom, it reminded me of the days of owning a reel to reel studio.
Sounded just like it so that's what I use now.

As Bob said, Slates VTM is the bomb...

I tried Waves J74 and liked it...but too expensive
even on sale.

IK's new Saturator X has Tape Emu also...

And the UAD Studder is probably quite good, but I don't own any
UAD plugins, so can't attest to that...

Waves Kramer Master tape is "Ok" but a CPU hog...

Ozone 7 Advanced's New Vintage Tape module is quite nice also...

VTM. Always. Sound.
But trying to swap for Ozone Vintage Tape. Thanks for reminding me, Larro.

Fleer
VTM. Always. Sound.
But trying to swap for Ozone Vintage Tape. Thanks for reminding me, Larro.

The physical iLok mostly doesn't work on my system. The dongle came up just long enough to move my licenses off of it, so...I have a bunch of Slate plugs that, for a consideration, I'd be willing to part with (VMR Complete (includes VCC), VTM, and VBC).
 
I sure wish Slate would permit iLok authorizations to a PC, like UVI and Softube. That works great for me. 

I put Slate's VTM on every bus when mixing. Then when I mix down all of my audio tracks to a new mix, I'll add one more instance, usually with the opposite tape type that I used on the individual mixes. I used to use u-he Satin a lot, but I found that VTM has a more natural sound. However, Satin is still really useful if you want a more colored sound, using it kind of as an effect. 

I use Waves Kramer Master Tape on my drum buss on every song and love the punchiness.

Guyz , don t forget in ozone that you have the exiter witch has several modes including tape , and you can have different mix per band !

I used to use Slate VTM on all tracks and liked it, but someone suggested I remove them from a mix and see what they were adding. The stereo field opened up considerably and things sounded more open. 
 
I do use UAD Ampex on the master all the time, and am now experimenting with UAD Oxide on tracks and buses, but not on all tracks or buses. For example, instead of using an instance on each tom track, I'm experimenting with just using one instance on a tom bus.

I love slate and use it often but I also really like Satin by U-He, it can get the creative juice flowing!