I've resisted having a master list of bug reports, but it does seem helpful. I've started three threads on theses forums.
Major Bug Report
The major bug report thread is for any errors that cause MTG Forge to crash or are a major implementation error. Examples would include attacking on your first time with a creature with haste, this will cause MTG Forge to crash, and creatures with shadow being able to block non-shadow creatures.
Minor Bug Report
There will be probably many of these types of errors. Examples of minor bugs include trample not working when there are multiple blockers and if the computer has two planeswalkers in play, you can only attack the one that came into play first.
Card Bug Report
This involves anything that MTG Forge does with a specific card that differs from what the card should be. Some good examples are Bottle Gnomes not having his sacrifice ability and Control Magic being an Sorcery instead of an Enchantment. I have put up a list of all known cards errors in this forum.
Hopefully having a list of bugs will making playing MTG Forge better.