Having played the iPad Galaxy Trucker app for a bit now, I can say that it's pretty great, for single-player anyway. It's a much more ambitious app than most board game conversions, more like an expansion or sequel that just a conversion. There's a campaign mode, there are additional cards, and there's an option for turn-based ship-building.
I've only played the campaign and only with the real-time ship-building so far, but that's quite well done. It works well with the touch screen. The campaign is fun, having you fly between planets doing quests, more like a full-fledged adventure game than just a series of missions.
I can't say much about multiplayer yet because the "Quick Duel" option didn't find a game for me, and when I tried making a game, nobody joined it, possibly because I set it to real-time ship-building, when all the games people were playing were turn-based ship-building, which I haven't learned yet. Anyway, it wasn't super easy to find a multiplayer game, unfortunately.
There are some UI design and game design quibbles I can make, but the good parts outweigh them. For example, one thing I didn't like about the original game is simulating events that end up doing nothing, like a meteor shower where none of the meteors even threaten to hit a ship (much less cause any damage), or a small meteor shower when nobody has exposed connectors. At least in the physical game, you can skip simulating a small meteor shower if you know ahead of time it won't do anything, but here the whole thing is animated through. Somehow this bugs me less than I thought it would, though.