According to an EHX article about Frusciante, he's used the Micro Synth on tour and in the studio.

"During the recording sessions for In Rainbows, the big box version of this pedal can be seen next to Thom’s Tech 21 XXL, so it is probably that he used it, though the parts recorded with it may not have made it to any of the final versions of songs."

Matthew Bellamy uses the Electro-Harmonix EH-7900 Micro Synthesizer, as seen on his pedal board in a photo from the Showbiz era on Musewiki.

These battles over creativity, keyboards, and Eddie’s status as a guitar hero continued into the 1980s. The guitarist penned some songs from 1981’s ‘Fair Warning,’ like “Hear About It Later,” on piano, even though he’d play them on guitar on the album. He did, however, sell the band and Templeman on an evil-sounding instrumental called ‘Sunday Afternoon in the Park,’ which saw Van Halen utilize an Electro-Harmonix Micro-Synthesizer for the track.

Trent Reznor is confirmed to use the Electro-Harmonix EH-7900 Micro Synthesizer, as evidenced by its inclusion in the partial list of equipment used to record "The Fragile," as detailed in the Fragility Tour program. This information is corroborated by the source, nin.wiki, under the section for Nine Inch Nails - The Fragile (halo).

In this 2014 photo posted by Corgan on his Facebook page, his setup can be seen, including the EHX Micro Synthesizer.

"Satch goes wild with gear and musical experimentation on Engines of Creation. The album's techno edge, sequenced rhythm tracks, and heavily tweaked guitar parts proved challenging in rehearsals. But because of his open-minded approach, and a willingness to let bassist Stu Hamm and drummer Jeff Campitelli re-purpose parts they could pull off live, Satriani has brought the way-out-there sounds back to Earth on his current tour. Here's a brief rundown of what he's using on stage.

Guitar.com: Did you have to bring any special gear with you to re-create sounds off the newest album?

Satriani: We tried. We used things like Moogerfooger pedals and Electro-Harmonix Micro Synths and Bass Micro Synths. You know, Hafler Triple Giant preamps. We used a lot of fun gear on the record. It's very pedal oriented. But I found in rehearsal that this stuff, when you turn it up really loud, it doesn't really hold up, and it doesn't project as much. And I thought, 'You know, I don't want people in the 30th row to be looking at some guy's head while he stares at his feet stepping on pedals all night.' So I said, 'I'm gonna do what I've always done; I'm gonna do what Hendrix proved could be done. I'm gonna make a really trippy record, then go out live with a really loud amp and a couple of pedals, and go for it.' You just make the music new again. You keep it simple.

So I found that I could use a Fulltone Ultimate Octave to replace a lot of the stuff that I used in the studio. And there is still one section in 'Borg Sex' that Eric uses the Electro-Harmonix pedal for, but he's hoping to replace it with the Fulltone pedal. The Fulltone pedal is a more straight-ahead pedal; it sounds exactly the same every night. The Electro-Harmonix are really unique, but they seem to sound different every night. And that can be a problem."

Kevin Shields uses the Electro-Harmonix EH-7900 Micro Synthesizer, as evidenced by a collection of his gear on Rateyourmusic. The source includes various pedals, showcasing his extensive setup.

You can see the Electro-Harmonix Micro Synthesizer is visible on the shelf to the right of the green pedals.

From Matty's May 29th 2019 instagram story.

Annie states that she uses this pedal for sustain during an interview for GuitarWorld.

"I think I was using an Electro-Harmonix Micro Synth. The new generation of Micro Synth has a lot of sustain. I used sustain on the record for things like the solo in “Rattlesnake,” which is all on one string. Just a big slidey thing."

Here's the photo of his EHX Micro Synthesizer:http://www.sonicyouth.com/mustang/eq/06lfx14.jpg