Including fees, i have spent 0.001962 to make a 0.0015 BTC transaction.
Your exact value and fee calculator told me that a 0.0015 BTC deposit would result in a 0.00128 withdrawal.
When i combine the output values of the two transactions funding my withdrawal address, i get 0.0012795... I know, it's only 0.0000005 BTC (50 satoshi's) less than you promised, but since you already take quite a hefty fee, i think that you should make sure the calculated output value matches the actual output value....
On top of this, splitting the output into two unspent outputs increases the fee i'll have to use to spend both by about 0.0001 BTC compared to spending a single unspent output (at current feerate).
This means that, after spending 0.001962, i'll get the equivalent of 0.0011795 BTC in clean, spendable funds...
I know why you don't allow people to chose the output timeframe, nor the number of outputs, nor the size of the outputs, nor the exact fee... However, i like to feel in controll... Personally i'd like to have some kind of "expert - i know what i'm doing" menu that allowed to to chose the size and number of outputs, the feesize and the delay.
Ending on a (very) positive note: i traced the outputs funding my withdrawal addresses and ended up on a poloniex wallet for one of the outputs, and an unknown wallet holding ~80 BTC after +1000 transactions... This means that your system is telling the truth and the funds are coming from a clean source.
This being said, it does look like you get a big unspent output from a "clean" source, and you keep re-using this unspent output to fund all mixing sessions...
It's like:
unspent output of 3 BTC from a clean source funding your address
unspent output of 3 BTC used to pay first client => 3 BTC in, 2.9 BTC to your change address, 0.1 BTC to your first client
unspent output of 2.9 BTC used to pay second client => 2.9 BTC in, 2.7 BTC to your change address, 0.2 BTC to your second client
unspent output of 2.7 BTC used to pay thirth client => 2.7 BTC in, 2.6 BTC to your change address, 0.1 BTC to your thirth client
unspent output of 2.6 BTC used to pay fourth client => 2.6 BTC in, 2.3 BTC to your change address, 0.3 BTC to your fourth client
The thing is: it will allow me to find other people that used your mixer, since i only have to follow the trace after my own mixing session. This is not a problem, as a matter of fact, it's pretty common to see this kind of behaviour amongst mixers, as a matter of fact, it's the same with chipmixer (if i initiate a mixing session and get my chips, i can now follow other people that used chipmixer).