I'm going to buy them anyway, but I want to know if they have the Lucasarts / Telltale approach, which is "Enjoy the adventure! We won't kill you and you can't screw up!" or the IF/Sierra approach which is "Oh, you didn't know that you ruined your game 3 hours ago because you forgot to pick something up which can't access now? I don't see how that's our fault!"
In other words, should I be paranoid and have three different walkthroughs opened at the same time hoping I'll survive the experience, or can I just enjoy the game and have fun? :|
I actually owned UAKM a lot time ago, but I never got it working right... I hoping the GOG version won't give me much trouble.

It's the LucasArts approach. Don't worry about total failure.
The Pandora Directive, however... from what I've played so far, you can royally screw yourself by not playing your cards right with the money situation... but I haven't played that much, so I can't properly determine.
I never had trouble with any of the GOG Tex's, so you should be okay.

No. You can't screw up with the money, you can always find more. And the games have built in hint systems so you won't need any walkthrough. There are, however , a few places where you can die, so save your game. But at least the deaths are more logical and doesn't come as much as a surprise as in older sierra titles. Get the games, you won't regret it once you get into the experience.

Thank God! And if they take the Wadget Eye game approach to detectiving, I think I'm going to squee!

in pandora if you forget to do something you just click on the travel & you are back to the place you need to be & then hit travel again. There are several endings depending on how you play the game & choices you make to what ending you get.

Mostly.. main difference is that while you can't really get "stuck" by doing something in the wrong order (as far as I know..) you can die by doing the wrong thing at the wrong time, or being a prick during certain NPC conversations. So saving often is always a good idea.
I remember being terrified of those roaming bots in the office levels in UAKM (or was that Pandora..?) back in the day as a young'n, just because the movement interface was so touchy..

There was a patrolling kill-bot in UAKM. I HATED that thing... most frustrating part of the entire game...

The Tex Murphy series (UAKM, Pandora, Overseer) are probably the best adventure games ever made, before the genre became unpopular. They are always logical, the objects to pick up is easy, because they look slightly different from the surrounding, so you don't have to click million times on the screen, if you don't want to. Although often it is worse it, because there are funny remarks about just about everything (if you do click). As another person wrote it, no need for walkthrough, the built in help system is perfect. I have the originals on CD, but they don't work on my new Vista based computer, so I was happy to find GOG's versions. I got so far UAKM and Pandora, they work perfectly well and playing them a decade later, almost as if I would play it the first time. They are very entertaining, and the money you have to pay for it negligible. Additional plus: you don't have to swap CDs, which was a bit irritating with the original versions (especially with Pandora).
Surely, the best spent few bucks.

I'm glad to hear this because being a Adventure game junkie certain games like Police Quest series made me pull out my hair with the whole oh you didn't take this one item that wasn't junk that would save yourself. Have fun restarting the game.

I just picked these games up from GOG after reading this thread. So looking forward to them. Is there a approx idea of playing time. Does each game take about 10-15hrs or so.

10-15 hours or so at the least, if youre lucky.
Now, granted, I was 10 when UAKM came out, but at 10-14 I was probably also at my peak of being good at point & click adventures.
If you actually PLAY the game, and dont sit there with a walk through alt-tabbed (although in game hints help, you shouldnt play the game with it open always) it should take a while.
I look at it this way, when people say they have 10 hours of gameplay nowadays, they think its good.
Back when I used to devote every free seond to video games, if you didnt push 50+ hours, you were junk.
And I loved these games

Yeah, it's pretty much the LucasArts approach, although I always wondered what would happen if you never picked up your pocket knife in The Pandora Directive on the first eight / nine days, and went to the Maya Temple without it, on the last day.
Don't recall that you had to use your pocket knife prior.

Yeah, way more - at least for Pandora. Enjoy every second because you'll be sorry when it's over. The good news, if you take you're time, you could clock in 30+ - I think I was like 50. But then again, I'm a slow gamer that likes to click on everything and listen to every line of dialogue.