[Tarislar]

Only time I've ran a GMPC was when we had multiple GMs that rotate through sessions.

Actually, I remember a group that did this too.
Basically no one really wanted to "GM" full time,  so we all had our own PC's & then the GM spot would rotate through "Modules" or when someone had their own adventure idea.  While you were GM that session your character was there but basically was hanging out in back that week letting the remainder of the group work their way through the mission w/ the GM putting his character in "Autopilot Mode" following the group around taking suggestions from the group.  Essentially being a "Henchman" for the week.  After that adventure, (1+ sessions) then someone else would step up for a while & take the helm.

[Lethal Joke]

The only time I've ever seen a GMPC team leader work is when that leader serves purely as a plot hook to introduce the players to the setting in a very specific campaign - cyberpirates, specifically. The captain makes the decisions for one or two sessions while everyone learns what the options are, and then s/he dies and hands over to a player. That's almost understood from the beginning. Hell, the plot might even be based around some pre-game agreement that "the PCs are going to be involved in a mutiny" sometime soon.
Or you could have a stand-offish corporate leader handing out missions, that's an old and proud tradition in Cyberpunk games.
Or even a Carter Burke style character there to screw with the PC team - basically another obstacle.
Those are some leader options.
As for the face...
No. Just no. That completely removes agency from the players. More to the point, that's going to result in GM talking to himself, while railroading the story. Nothing good can come of it!

The leader thing makes some sense to me, though I would think a permanent, loyal fixer rather than a true GMPC.

In terms of GMPCs, they're there to fill a role nobody wants to play. I, personally, have been offering riggers-for-hire to round out my gaming group - which is me as GM and three players.

The face? Inexcusable. None of my players is a face - so they just have to muddle through without. The elf street samurai does most of the talking due to his corp etiquette and negotiation skills.

I will admit to "talking to myself" a bit as NPCs. I spelled out for the PCs that they are present and may interrupt at any time (consequences vary.)

[incrdbil]

 I am in a game that seems challenging.
We have 7 people plus the GM at the table. We are new to 5th edition and a couple of us haven't player since second edition.

We started the game as a corporate team and the GM set up a character in the group as the team's leader and the team's face.

It doesn't seem to be working well, however I also may just be biased since he had me re-write my character who was designed to be a shaman with strong secondary face to drop my leadership, negotiation and etiquette skills.
Anyway, I am curious what other GM's experiences have been like running characters as part of the team.
Thanks

I feel 7 people is too large a group..and that's without the GM adding a character. In such a size group, the GM has no business running a character, and in any size group, a GM 'PC' should never, ever, be the leader/face. 

That's simply wasting too many role play encounters that should be reserved for players, not subjecting them to sitting and watching the GM have conversations with himself or rolling dice tests between his so called PC and NPC.

The fact he forced you drop a role you wanted that he shouldn't be doing indicates he's being selfish, and that's a poor GM, IMO.

As players, you should get together, and tell the GM you don't want him to run a character, much less the face, and even if a GM has an NPC, players should get first pick on the team roles they want to fill.

The characters can always, in game, choose to exclude the GM's NPC on runs as well..but frankly that will just lead to a toxic GM vs PC atmosphere, so I'd talk to him first.

[Adeptus Technicanus]

Only time I've ran a GMPC was when we had multiple GMs that rotate through sessions.

Actually, I remember a group that did this too.
Basically no one really wanted to "GM" full time,  so we all had our own PC's & then the GM spot would rotate through "Modules" or when someone had their own adventure idea.  While you were GM that session your character was there but basically was hanging out in back that week letting the remainder of the group work their way through the mission w/ the GM putting his character in "Autopilot Mode" following the group around taking suggestions from the group.  Essentially being a "Henchman" for the week.  After that adventure, (1+ sessions) then someone else would step up for a while & take the helm.

My group used to run two seperate games, switched out every other week, so that the DM could get a chance to play and not get burned out. This also allowed the GM's more down time in between sessions to produce a stronger story. This was my Thursday goup, my Sunday group (Back then I gamed Wed-Sun every week, excluding work) would trade off games between two GM's each month, for a better continuity. Friday's were similar to Thursdays, and I ran every week on Wednesdays. Our groups were 6-10 players, normally, and one campaign I remember the DM was running GMPC's, but they were plot devices, never took the center stage that I remember, except when their plot happened. Red Wizard GMPC ended up with the Half-Elf PC and the dwarf GMPC was actually part of the Anti-Party. Left us with a Human Rogue-Fighter(?) GMPC, who never did anything memorable.

I have a Detective GMPC for getting the ball rolling in an Adventure if need be, (Getting a group of 1st time Shadow Runners together, so am planning on the Beginner's Adventure for S&G's/Training) but will probably not use him, as he is a left over from a previously abandoned campaign concept.