Don't you hate it when...
You get asked by a race to trade your whatever for their Impulse Engines. You agree, and when you go to check the tech tree, you realize that you already had Warp Engines which you traded from another race a while ago!
The obviouse solution for this is to "reject" an offer, run and check the tech tree, then go try and get the same deal. This, of course, often fails because the offer has been taken off the table.
Having access to the tech tree and starmap would really be helpful.
