I think if I'm holding on to a TB or Geocoin for a couple days then it should automatically be placed/recovered from every cache I visit from the time I pick it up to the time I place it... that way, if I'm on a long road trip then it doesn't just jump from one place to the other, but you can actually see where I took it.
Also, the "cache found" entry form should also let me log any TBs/coins right there, with a blank for the tracking code. I hate having to log all the caches, then go back and log all of the trackables afterwards... or, if I pick up a trackable and say "Retrieved from xxx" then it should automatically log a visit to that cache.
Also, it should be easier to say that a TB/coin is not in a certian cache. I like to let people know that their cache does not contain the trackables that it claims to, but when I do so then it is added to my "discovered TB/coins" list. I think when I log a cache entry there should be a list of checkboxes for each TB that is supposed to be in the cache and I can uncheck the ones that I did not find in the cache.