I've read through Mongoose Traveller and am very impressed. It's close to Classic Traveller -- close enough that I could use any classic Traveller adventure with it with no extra effort to speak of. It has a lot of minor differences from Classic Traveller, but they are mostly very minor and are often actual improvements instead of just differences to be differences. It is harder to kill off a character during character generation, however. In fact, it's impossible without an optional rule. I can forgive this, I think.
I haven't played it, but it looks like a game with a lot of "old school" feel that I would enjoy playing as much as I did the original.
Here's a list of differences between Mongoose an Classic originally posted by aramis on COTI:
Differences:
Character generation
- more careers than Bk1, fewer than Bk1+Supp4
- no reenlistment rolls (low promotion rolls get you the boot)
- added event rolls
- background skills
- point based option
- Ironman Option: failed survivial kills, but each term is one reroll per session!
Task System
- an explicit task system exists
- the system uses a stat DM raning from -2 to +3
Travel -
- prices per parsec
- generation method of passengers, freight and cargo
- chances of misjump
- risks of jumping from within 100 diameters (much less dangerous than CT)
Equipment
- added cybertech
Combat
- All damage to End until End gone (Makes characters much more fragile, IME)
- armor reduces damage
- lots of xdy+z damage codes
- Amount of excess on to hit adds to damage
Worlds
- effects of Law Level expanded WILDLY (Essentially making anything over LL6 radically dangerous)
- a number of additional bits of information
- options for tailoring
Ship Design
- Basically bk2 but...
- sizes covered in core dropped to only 2KTd
- bay weapons added
- additional types of energy weapons added
- computers take no space
- bridge no longer formulaic; ≤200Td is 10Td, 201-1000Td is 20, larger is 60Td
- optional drive modes (and poorly executed, some of them)
Ship Combat
- not drive letter based for damages (but was in playtest - grab the playtest draft, it's better)