One can sum up almost everything from JG thusly: "Interesting idea, poorly executed." They tended to waste too much space on randomly generated NPC and creature stats, which you could easily do yourself, and skimp on story and setting, which are what you're generally looking for when you buy a prepackaged "adventure."
Amycus Probe, Rogue Moon of Spinstorme: Interesting ideas poorly executed. These were tournament scenarios, so they're short. Basically, you explore some alien ruins and don't find much of interest. Rogue Moon is the better of the two. Of everything on your list, it comes closest to being a fully-developed adventure.
Darkling Ship: no experience with this one.
Doom of the Singing Star: Another not-bad attempt. Huge maps of a ship that has rather illogical layout, but still -- huge maps. Some interesting scenario ideas, but that's all they are -- ideas. As usual, way too many NPC descriptions.
50 Starbases: Useful if you intend to run adventures centered on starbases or similar types of installations. (Nothing says that these things need to be only starbases. They can just as easily be mining colonies, small military bases, etc.) Some of the maps are excellent, some are execrable, most are OK. Some of the maps are hard to read because the hex grids are so dark. Still, this one is generally worth the money.
Dra'k'ne Station: Interesting idea, poorly executed. Another big alien installation to explore and find next to nothing. This one has good potential, though, if you put some effort into it.
Simba Safari: Basically an interstellar hunting expedition. If your players like traveling to distant planets, encountering exotic lifeforms, and killing them, this is the adventure for you. As usual, there's something really cool to discover, but the 'adventure' does exactly nothing with it. The included ship layout, however, is pretty good.
All of these fall into that category of supplements that can be excellent if you do all the work turning them into something. If you can pick them up cheaply, they're worth it. Don't pay "premium" prices for them.
Steve