I really enjoyed LASH, and would rank it up with the best modern IF I've played. Other reviews have complained that it just doesn't quite hit the mark for them, and I understand a least somewhat where they're coming from, but for me the impact of the first 4/5's of the game was undiluted by the problems I have with the ending.
I like the fact that the "treasure hunt" aspects of this game are used in the service of the greater plot, and are well-motivated. And then once you finish up that segment of the game, you have a good idea of the geography you'll be dealing with in the next segment.
I appreciated the multiple different endings (including the nested ones) and the obvious care and craft that went into this title. It was obviously well-researched, well-written, and well-implemented. The opening background material and the help menus really helped set the initial post-apocalyptic tone, and I kept expecting the promised bands of slavering mutants to set upon me at any time.
The impact of the ending of the game hinges on several factors: You have to preserve a distinction between the player and the protagonist; you have to have emotional resonance built up in the second half of the game; and you have to (Spoiler - click to show)transfer sympathy for the plight of the slaves to the "plight" of your MULE.
I thought the distinction between player and protagonist was well-established through use of first person perspective (paradoxically more distancing, as others have observed in the past) and specific error messages that emphasized the robotic nature of the protagonist. Shorting out "x me" was also a nice touch.
I also thought the simulation section did a good job of furthering this distinction, using the mechanism of the bracketed comments from the robot.(Spoiler - click to show) I found myself strongly identifying with the simulated slave, to the point that I felt very much on edge while sneaking around to get my supplies for the escape. When you're in the room off the kitchen, with nowhere to run, and you hear the Master's feet approaching? These types of scenarios were very well done and left me feeling trapped and panicked.
As far as depth of characterization goes, I felt that Momma and the Master were well-written given their roles in the story, but I never got that feeling from Matthew. He seemed insufficiently motivated to me, and mostly seemed to exist to recite pro-Abolition lines to give his father something to tee off on.
Unfortunately, successes on the first two points were rendered largely irrelevant(Spoiler - click to show) by the failure to facilitate transferring the emotion generated by the mistreatment of the slaves in the second section to your MULE in the third.
The robot was nothing but an emotionless perfect servant during the first part of the game. Granted, the documentation talks about it being part-organic, but it didn't really act like it. It interacted with the world in an emotionless state that didn't really do much to make you think that it was a feeling being with rights that should be respected. After the simulation, it did start expressing more of these feelings, but all that did for me was to establish cognitive dissonance and make me confused. In fact, the first time I played, I just ran down to the airlift platform and ordered an airlift, never having received any of the balking messages it mentioned in the ending blurb, so it just confused me as to why I was suddenly the bad guy.
I would sum up LASH as a brilliant concept implemented in a just-short-of-brilliant way, or a brilliant game with a misstep at the end. Still enough for a 5 in my book.