I have transition exactly 2x...And i just did a major BC on 12/21/08.
Transitioning-
Pros: Length & more Length

Moisture. Gives you time to think.
Cons: Your hair can actually
become unhealthy(if that makes sense) because of the 2 different textures, that can do some damage if you dont know what your doing.
^^False texture- that isnt your real texture most likely you curl pattern is much tighter.
Detangleing
Waiting.
Temptation to relax. You still have to
chop something off so whats the point of waiting??!
Big Chop-
Pros:
No waiting.
Your actually natural within an hour or two.
Cons: Its like
Opening a gift- you dont know what your going to get because well you never rly had it before, so you will probaly need much better products & methods then you had before.
Short hair, unless you do not have alot of shrinkage or waited like 2yrs to BC then your hair is going to be short. Getting use to the
dryness, IMO i think natural hair can be much
dryer then relaxed hair.
I think thats the only way i can put it. And even though i love long hair i wish i would have BC 2yrs ago instead of waiting for it to grow out(gosh i could never imagen myself saying that

).