Well, that's a matter of opinion as to what is considered a demo. I don't consider any of their demos long enough (ie, full of sufficient enough content in regards to what they are actually selling) to live up to the term.
But luckily for me, my sister bought the set from Telltale and is basically giving me access to the game. So now, if I like it, I'll buy it. But if not, at least I was able to make that determination based on sufficient amount of information. And without having to resort to more illegal methods!

So, do I buy from Telltale or Steam?
Even though I've recently enjoyed slagging off the digital distribution service I have 200+ games on, Steam are throwing in a Wallace and Gromit episode if you buy the complete Tales of Monkey Island package....

Well I did think that was a good deal but the last time I loaded the telltale site, it implied that you could still get the code for a free game if you buy the MI season. Personally I'd sooner buy from the makers directly

I'm really liking it so far. I've never played any of the previous games so I wasn't sure how the humor would work but I like it. The puzzles are really interesting and one in particular is one of the best puzzles I've solved in a long time.
However, I do have a couple of nitpicks. One of the puzzles has an annoying tendancy to change camera angles when it would be easier to solve without the camera angles changing. Also, I want the old point and click walking back. WASD isn't bad, I just like the clicking better.

Which one was it (in vague spoiler free terms of course)?

Telltale. If you buy it from Steam you don't get the excellent after-sale support.
Also if you buy the whole season on Steam, Telltale won't be able to track your purchase and send you your DVD at the end (if you choose to get one).

I second that! It's great! I'm trying to take it slow and savor it. It's going to fast.

telltale says u can pick any free episode of any of their other games...

Any free episode... TellTale it is!
THNX.

All your positive comments convinced me. Downloading right now.
[EDIT] Okay, immediate first impressions...
1. Multiple dialogue choices that all result in the same thing being said: Annoying. It's fun as a joke every once in a while, but this is all... the... time!
2. I'd like to find the guy who decided that randomly changing camera angles, usually hiding the objects you're supposed to interact with, was a good idea, and shoot him through the head! Or my personal favorite, have him trampled to death by ducks. That "feature" sucked in the original Alone In The Dark, and it still sucks now.
3. The guy who designed the inventory also deserves at least a good kick-inna-fork. "Let's see, it's always been dead easy to use one inventory object on another. Let's make that more difficult and annoying, shall we?" What the hell is wrong with picking up an item from the inventory and using it directly on another? It's worked in every other adventure game I've played where that option existed at all.
Other than that, the game seems to keep most of the style and humor of the earlier games. It does seem that any player action leads to quite a bit more scripted action than usual, which is a bit annoying. There also doesn't seem to be the same degree of freedom that you had in the earlier games (go anywhere, look at anything, even objects that don't actually serve any function in the game), but then I've just started the game, so hopefully it opens up a bit more later on.

The second jungle one.

Yikes man, even I've played most of the adventure games out there. Let me just say static rendered adventure games suck, Myst included. Okay now that I've gotten that out of my system. I try not to dissect a game unless it starts off with either a glaring bug or crummy dialog, aka Jurassic Park Traspasser. I tore that game apart. Now adventure games are linear, you can't get around it. Everythings always the same and leads you to the same conclusion, even adventure games that claim multiple endings. You play it because the story interests you and the puzzles are like a piece of candy. You work hard to solve the problem and it could go either way of a treat or more problems to solve. That's the beauty of playing an adventure game. It might turn out different because it's interactive but it never does.
Monkey Island is like a constant flow of glucose into your vein. Fun to play and fun to solve puzzles and you even get rewarded with cut-scenes. You couldn't ask for anything more, well I guess you could. Then you'd be walking the plank matey.
Alone in the Dark was a good game, it scared the crap outta me when I was a kid. The puzzles in it were tough. Now that we have Resident Evil 24 or whatever number they are at right now AITD doesn't seem like a big deal.

O...kay. What does static rendered adventure games have to do with this?
I don't really know what you're trying to get at here. The original MI games weren't all that linear. The story was, yes, but not the game itself. You could go pretty much anywhere (in the "sector" you were in at the moment, e.g. Melée Island, Monkey Island, etc.), and you had some degree of freedom to choose the order in which to solve certain tasks. Actually, most adventure games I've played are like that.
Fortunately, as I played a bit more, the game did open up somewhat, at least regarding movement. The order of tasks seems rather more constricted than in the original games though.
That's all well and good, but that's not what I was talking about either. AITD had the same "let's switch the camera angle around between ones predefined by us, many of which are completely debilitating to the gameplay" mechanic that this latest MI incarnation suffers from. I remember places in AITD where you would be shot at, by someone standing outside your field of vision, for instance behind a hedge or something, making it impossible both to move out of the field of fire and to shoot back. This because of the stupid predefined camera angles, and given those, the poor placement of the enemies.

Included? Don't you mean 'especially'?