I enjoy exploring the worlds and reading the lore. I love the idea of having a codex / encyclopedia galactica / hitchikers guide to the galaxy, but I find it extremely frustrating that it can't be completed / unlocked completely.

Map Exploration Frustration

• Mountains and un-traversable terrain shows up as empty hexagons until the entire area has been explored. I like to try to unlock the entire map, but when these things exist, its not obvious which parts are unexplored, and which parts are simply unreachable. If the area is simply unreachable, then it should be revealed with one of the adjacent areas - not with finding the last discoverable area.
  
• Exhaustion zones are not indicated on the map
  
• there should be a planet achievement for unlocking the entire map
  

Codex Frustrations

There are too many bugged codex entries (see this thread: http://www.swtor.com/community/showthread.php?t=104803). Before I came to this realization, I tried to find everything on the first few planets, and just ended up wasting time.

• Its not always clear how to unlock something. Do i need to complete a quest? Choose the right dialog in a conversation?
  
• bestiary discovery seems arbitrary. Sometimes its the first time you see one of those species. Sometimes it seems like you have to kill a certain amount, or kill one in a certain area, or maybe you need to kill one of each variation of that species, or a specific elite version. So far, I don't see a pattern. Sometimes, no matter how many you kill, click on, run past, you never "discover" the beast.
  
• Some datacrons listed in 1 planet's achievement, are physically located on another
  

Suggestions

• modify the codex to have be checklist for all the specific things in each category (notable people, beastiary, species, etc...). The guide might not reveal the exact locations of datacrons and the world boss, but it should give general clues / hints (and include region / sub-region) on how to achieve each goal. If it requires a quest chain to unlock it, indicate who the quest giver is in the clue, and there should be no level cap on starting the quest.
  
• Instead of making this the default behavior, maybe there could be a tourism vendor on each planet that sells a "tourist guide" that contains hints on the planet's codex entries (e.g. unlocks the checklist)
  
• a tourism vendor could also sell special items to individuals who have explored most / all the planet has to offer (maybe food that is slightly better than the cantina food
  
• make a legacy codex, so that one legacy could unlock the entire codex - including both faction and class specific lore. Each character would have its own codex, but the legacy would track the aggregate of all characters.
  

Map Exploration Frustration

• Mountains and un-traversable terrain shows up as empty hexagons until the entire area has been explored. I like to try to unlock the entire map, but when these things exist, its not obvious which parts are unexplored, and which parts are simply unreachable. If the area is simply unreachable, then it should be revealed with one of the adjacent areas - not with finding the last discoverable area.
  
• Exhaustion zones are not indicated on the map
  
• there should be a planet achievement for unlocking the entire map
  

I agree on the last 2 points and I used to get frustrated by the impassable terrain hexes, till I noticed that, pretty much in all cases, the unlockable areas are a lot bigger than 2-3 hexes, and are all in light grey, whereas the impassable ones are dark at some part of the vertices. (Also, you can double-check whether the area you are trying to reach is actually reachable or not, because you can run up against the "walls" of the impassable area, and your "location" changes from being the sub-zone you were in, to being the generic map name (e.g. from "Tythos Ridge" to "Tython") and this comes up in the middle of the screen, so you know you don't need to waste any more time trying to get there.

Once I spotted this, I was able to unlock all the world maps fairly quickly (the one exception being the Coruscant Spaceport, which still requires that ridiculous trick involving climbing up one of the sloping supports that are in each of the docking bays, to stick your head through the roof).

Excellent suggestions for codex entries! I really like the "tourist" idea. Hell, maybe BW could make a special title out of it, like "tourist", "globetrotter", "trailblazer", etc.

As for knowing which areas of the map can be explored, it's actually quite easy: areas that contain hexagons with barely visible outlines are impassable, while those with hexagons featuring bright blue edges can be unlocked. Fatigue zones are generally on the outer edges, anyway, so I've never had a problem with them.

Thanks Ancaglon & Jeffko for pointing out the map tile hints. This will reduce some of my map related frustration

It would be nice if these subtle differences were more obvious. I run around with the translucent overlay, and depending on the scenery, the differences range from undetectable to barely noticable, though I can see them when I stop.