In case this hasn’t been posted before, watch and learn.
How about you tell us something we don’t know 
These tunnels I’m working on are 512 units wide. Betcha didn’t know that.
Having replayed Opposing Force recently (read: yesterday) and looking at it with a critical eye… I’d say the Operation: Black Mesa team have their work cut out for them. The game’s plenty cool, but Gearbox did a pretty sloppy job justifying events and created a rather confusing trek through the Black Mesa facility. The easiest example I can think of is Gordon Freeman travelled what feels like half a mile along the transport system from where Adrian Shepard intersects with the course of Inbound. From the Sector C Test Labs and Control Facilities, Gordon had to spend something like three chapters - Unforeseen Consequences, Office Complex, We’ve Got Hostiles - to reach the surface. Shepard reached that point in the transit system by going down three ladders and slightly sideways from his surface crash site. I’m having some degree of trouble picturing the Black Mesa Research Facility layout with these two accounts in mind. Opposing Force has this knack of going from offices to sewers to offices again then to the surface and then to On a Rail, essentially. That’s not a bad thing, mind you, but it’s not handled very naturally in Opposing Force and I’m thinking the Operation: Black Mesa team will need to put quite a bit of work making the transitions feel smoother and easier to follow.
Then there’s the issue of exactly why security guards are helping Shepard despite him being essentially just another one of the soldiers who’ve been slaughtering them since We’ve Got Hostiles. Opposing Force never makes an attempt to address this, other than casting all the guards as fat stupid stereotypes we’re presumably going to assume just don’t know any better. I can buy the scientist in Welcome to Black Mesa trying to help the soldiers. Presumably, they don’t know these guys are under orders to kill everybody, they just found them torn up in the doorway, so they assumed the US army is here to rescue them. The first fat guard even comments that “I heard a rumour you guys aren’t actually here to save us.” Fair enough. But then why do guards in other sections of the facility not immediately open fire on Shepard, or at least threaten him? That’s where custom dialogue could explain that. Stuff along the lines of “You’re not like the others. If you wanted me dead, you’d have shot me.” or “Look, I know you’re under orders to kill me, but if we don’t work together we’re both dead!” or something. There are ways around it, but it’ll take a bit of trying to fix it.
And then there are the plot holes, or at least plot threads. The G-Man at the end talks about handling witnesses, which is why he’s detaining Shepard. In fact, he talks like he’s a literal G-Man - a suit from the US government trying to cover up the incident. I suspect Gearbox weren’t given a copy of Valve’s “story bible” for Half-Life and they went from what they could deduce from playing the game. It made sense back in 1999, before we know that the G-Man’s employers were something else entirely (I still don’t know exactly) and that he was seemingly setting up the Earth for the portal storm. What, then, did Adrian Shepard witness that made him a threat where Eli Vance, Isaac Kleiner and - lest we forged - Alyx Vance didn’t? That brief glimpse of Gordon Freeman jumping into the portal? And why did the G-Man reactivate the nuke which blew up Black Mesa? As a government agent he would be motivated to delete the evidence. As someone working for a higher authority, he’d know that this would do nothing and would, in fact, prevent the Lambda Team from closing the portal. He refers to the bomb going off as the situation taking care of itself, but Half-Life 2 tells us that it didn’t! Seems to me like the G-Man’s final dialogue might require a significant re-write, or at least massive re-wording.
All of the above is solvable, however. It means more work, but it’s not a show-stopper, luckily.
edit
And I’m interested to see where the team take the new, clearly non-Xen aliens that Opposing Force features. Specifically, the “Race X” ones. That seems like it might be a nice fit for the overall Half-Life 2 storyline and might actually explain why the G-Man wanted to blow up Black Mesa. It might not stop the Portal Storm, but it’ll stop this other, completely unplanned invasion that was threatening to muck things up for everybody. Interesting…
Yeah, he doesn’t immediately shoot them.
That could indeed be a factor, he may also be known as being a really nice guy which is something that isn’t touched on in OP4.
I believe it is our duty to explore this side of Adrian Shepherd, a marine who paints pretty trees with Bob Ross, a man who finds the squirrel his acorn, a guy who is there when you need him.
Adrian Shepherd, marine, painter, squirrel friend and lover.
I’m in love already.
Oh god, now I want to do a Bob Ross playthrough of Op4.
Resonance Cascade = Happy Little Accident
Their website is off (not offline, but you can’t view anything) for a few days already. I wonder what happened.
Tis a mystery for sure…
Yes, how absolutely queer.
Probably a website rework.
I wonder if something´s gonna happen in their website tomorrow. You know, tomorrow being op4´s 16th birthday and such. I dunno… maybe I´m overthinking it.
Wild speculation on nothing like that are how people end up disappointed.
True but like you said, just wild speculation, not impatient hoping. When I first heard about Black Mesa, I didn´t set any expectations about it´s release date and when they announced it, it was an awesome surprise. With OBM I´m gonna do the same and just play with thoughts 
Hey everyone, the guys behind OBM and GD posted their latest artcle with the new screenshots in regards to OBM and GD on Moddb:
https://www.moddb.com/news/life-signs-2015
Yep, we finally came out of our shell and posted a media update, see you all in 3015
You can’t just confirm a release date like that! I don’t think we can make it that fast and now they’ll expect it then!