As Chrisss says, it's chronologically HL 1.5. I'm guessing now they've built the engine and all the assets for VR, HL3 could be implemented as another VR game, or even a DLC, with comparative ease. I think they'll want to do it too, for the sake of completion of the series. There's also talk that HL2 Chapters is going to be re-released for VR.
I'm now 9 hours into Alyx, by far my longest play sessions. I haven't used my headset a great deal recently and I have been experiencing the real life vs VR strangeness again. I was going to bed the other night and I could see the blue grid from the play space boundaries when I shut my eyes. And last night I got into bed and thought I was wearing the gravity gloves and went to take them off.
The game is stunning. The sound and visuals of the environments are amazing, and there are some proper scary moments.
My most sensorily confused moment came in (ironically) A Chair in a Room: Greenwater, when I tried to sit on a virtual chair. Very uncomfortable. Incidentally, I recommend Greenwater too, if you don't have it already; not perfect and a bit long in the tooth, but well-told, intriguing and scary as hell.
I went back to the start of Is or Will Be and retreated to the Barnacle room over and over again to kill all the headcrabs, saving my bullets just for the headcrab zombies. Just as well when I came across the Combine soldiers later in the level.
Haha, that sounds dangerous. Did you fall flat on your arse? :D VR can have some bizarre effects. I've nearly fallen over bending down and trying to stabilise myself on a nearby wall. There's a bar in Alyx and I really wanted to take a seat and pour myself a drink.
I do have A Chair in a Room but I haven't got very far. I found it a little frustrating, partly the Index controllers trying to emulate the Vive controllers. When Alyx is done I will try it again.
Have you got to chapter 7 yet? :O Oh my god that is some tense crazy shit going on! I had to take a break at one point and lots of swearing!
I haven't found the game particularly difficult. The enemies are pretty predictable (combine are mostly shoot, pause, shoot), head crabs are less jumpy and slower that they used to be, and J*** **********.