Given that I have had exactly the same problems with the Impulse version as other people have had with the Steam version and Gamersgate version, I think I can safely say that the problems people experience with Lionheart has absolutely nothing to do with which distribution version they are playing, vaalen.
Of course, I haven't tried the latest patch as it hasn't been released on Impulse yet, but I have no reason to believe that it it will resolve the frequent crashes I suffered from when I still cared enough to try to make the game run in the two months after I bought the game. Neocore is undoubtedly doing their best and if they just continue fixing crash bugs one at a time we might end up with a stable version a few years in the future when their game engine is used for in the third or fourth incarnation. (Note, however, that their previous game King Arthur still suffers from the same type of crashes after god knows how many patches, though it suffers from fewer of them, so I wouldn't bet on it).
Try it out, vaalen - you might very well be one of the lucky ones. But I would definitely download the demo and try it out first, if I were you. If it doesn't crash when you complete the included demo mission (crusader mission 1), odds are that you are one of those who'll have few problems with the game.