Hmm. There are several things in this class that sets off the 'ole unbalace-dar.
First is the relatively low level this otherwise super powerful class can be attained. A 4th level Human Paladin could technically fulfill all of the requirements, allowing entry into the class at 5th.
At 10th level a Monk gains the ability to penetrate DR +1 (Ki Strike +1) a Sacred Fist gets the same ability at 1st (which would be 5th total for Joe Paladin) and this ability increases very rapidly.
In addition, the 8th level ability (No Shadow Blows) basicly makes the Sacred Fist's fists magical weapons of the characters Wis modifier (!!! it is very easy to max the hell out of your Wis and get the equivalent of an Epic Weapon bonus with this ability) and that plus stacks with Puissant Blows (their version of Ki Strike, note that a Sacred Fist will never ever have to deal with DR. With a not at all unreasonable 18 Wis, this character will be going through +8 DR like butter.)
And of course then we have Sacred Flame. This basicly gives their fists the Flaming magical weapon ability, altered to do half sacred damage. In addition, this ability does the Sacred Fist level + Wis bonus in damage. Note that when this ability is active you are double dipping your Wis bonus, gaining it twice to your damage.
Its not all good though. Monks obviously get more attacks with their better attack progression. They get faster movement. Improved Evasion. All of those nifty Monkly things. Better saves. The Sacred Fist gets some spells, but they didn't seem too good.
Monks and Sacred Fists have close to equal damage, except that the majority of the Sacred Fist's damage is from static numbers while a Monk's is variable.
eg. A Monk might do 1d20 + 10 while a Sacred Fist would do 1d10 + 20. Average the same, but in game is a bit different.
Overall the Sacred Fist is kind of like a Monk on steroids. Doesn't have a lot of the mobility powers of the Monk but if he connects, you WILL go down.
I would really want to see him in action before making any big judgements like banning it or something, though.
Hope I helped!
