please go to sithwarior forums, you will find all formulas/caps you can imagine
to summarize (this has been extracted from game files and tested million times over):
1. there are no soft or hard caps
2. there are no rating caps
3. there are only percentage caps (but due to exponential scaling of rating to percentage, you would need infinity of each rating to hit the cap, due to rounding you will hit the cap at around 50k rating)
4. caps stack with each other, buffs/talents have no caps
current caps for ratings are:
crit% from crit rating: 30%
crit% from your primary stat (willpower for sorc): 30%
alacrity% from alacrity rating: 30%
surge% from surge rating: 50%
expertise% from expertise rating: 20% (was 9% in early beta)
defense% from defense rating: 75%
and so on...
Please note that caps stack with each-other (an ok sorc will have ~15% crit from willpower, ~15 crit from crit rating and another 10% from buffs/talents, for the total of 40% crit, but it is impossible to have more than 30% of crit from either willpower or crit rating)
Total percentage= SUM(all caping pecentages from ratings/primary stat) + base stat (i.e. 50% for surge) + talents + stacking buffs
Prior to 1.1 you could have insane amounts of expertise, but they removed the buff stacking (you could have ~15% from rating + 15% from stim + 30% from wz buff item, etc. )