Try out any other demos since your mega-post that are worth mentioning? Mine arrives tomorrow, so I'm downloading things now.
Let's see, I have done quite a bit more. I've been dropping impressions on one or two demos at a time in some posts since then, but here are some more thoughts/standouts:
HL2 continues to get better and better. The immersion is just eerie sometimes. Shooting through the trainyard area and the sewer systems was incredible. The pistol reloading animation alone is entertainment for the eyes. Aside from the benefit gunplay gets from having de-coupled head look and gun aiming, being able to whip out the flashlight in a dark tunnel and aim it seperately from your direct line of sight boosts immersion 10 fold. I also love how the crosshairs work in 3D now, basically sticking against whatever object your gun is aimed at, whether its 5 feet away or 100. Going up and down ladders is one of the only things that just doesn't feel right at all. Haven't gotten to play as much of it as I'd like to. But I've been trying to ration it to myself because it's so damn good and I want it to last forever lol. I'm about to get the hovercraft IIRC.
Proton Pulse - this demo might be the best starting demo for the Rift. Everything about it just works perfectly (except for that slow yaw drift). No fiddling with a keyboard and mouse you can't see. No worrying about tangling the wires of your gamepad and the rift. Everything is controlled by your head. The visuals fit the rift perfectly, clean and vibrant. Nothing is muddy or unclear. This game really feels like being transported to the VR of the 90's, and I mean that in a good way. Crazy pulsing neon lights, hyped up techno music. It's perfect. The game itself is very familiar territory, but controlling the paddle solely by looking at where you want it to move is soooo fluid and natural. You aren't moving so it's a great way to ease into VR optics. I didn't think I'd care for this demo much but it blew me away.
Hotel Apartment - No gameplay here, purely an architectural rendering. The graphics here are really nice even on a regular monitor, and in the Rift they really shine, even through the terrible resolution. The polished chrome fixtures look particularly impressive.
Ocean Rift - Great little exploration demo. Looking up at the life sized sharks and whales swimming above you is intimidating. The schools of fish are beautiful to watch. Good sound and visual design everywhere in this. Plus there is an awesome surprise waiting for you down in the deepest trenches....
Junglepack Dino Demo - This one is a mixed bag. On one hand, the visuals are great. Dense jungle setting, giant prehistoric trees, it's got a great vibe. However, the "tour" you start being guided on is horribly glitchy and just confusing. You start standing on the bed of a truck, which suddenly lurches forward to a Triceratops. Cool to look at but it has a repeated canned animation. The first time it completely glitched and the truck just never started moving again so I just hopped off and started walking instead.
Basically its glitchy as all hell, BUT the payoff is the life sized T-Rex at the end of the trail. Good lord does that thing look scary as you approach. Now, the demo was glitched and the T-Rex wasn't moving. But as I slowly crept closer I found myself downright afraid of the possibility of this thing suddenly springing to life and attacking me or something. Luckily, it didn't. I walked all the way up and stood directly underneath of it and looked straight up at it's mighty form. Simply amazing. Then I somehow got stuck inside a shrub directly under his dino-crotch and decided to call it quits.
SNES9x - Super Nintendo Emulator got rift support! Spent a few minutes playing Super Mario World and it was cool. Basically looks like about an 8 foot tall screen floating a few feet in front of you. The image looked great though, and of course the games are still fun. I want to see some themed spaces to accentuate the emulated games though, that's what could make it a unique rift experience (kind of like the City Quest demo).
I played a lot of other demos that were nice, but most of them are just more simple renderings to look at, not much to say about them. Hotel Apartment stands out because of how high quality the rendering is.
There are a couple demos I still have yet tall to try that most people seem to like, like Planet 1, Alone in the Rift (I'm too scared lol), Qbeh, among others. At this point I'm actively trying to limit myself so I don't blow through all of the available content within the first week.