Thanks for the input. I hope this answers all questions appropriately:
Trust is definately a key question regarding mixers. We thought the only way to build trust is to offer a reliable service, get good reviews by doing so and therefore more users which again vouch for us.
We landed on a few scam sites ourselves and thought that there are only few good options out there. Especially if every half year one of the large trusted mixers vanishes, there is place for new sites to replace them.

We did not start with an aggressive marketing campaign (unlike other sites ) because we think that trust only comes from getting a good standing in the community. Nevertheless we have a few people using our service everyday and until now everybody was happy with it.

Regarding the difference to other mixers, most of our features can be found in some other mixers, but we could not find the perfect service yet. Here are just a few examples after going through other mixers briefly:

• Chipmixer.com and Coinmixer.se use javascript on their sites, putting users at unnecessary risk. Although the mixing part of these sites seems to work if I go to their sites an Tor and disable javascript. Cryotimixer.io does not even work without javascript. We don't use Javascript at all.
• Coinmixers fee is 1-3% (random). I would not like to pay a 3% fee if I am mixing bigger amounts of Bitcoins.
• I think the mixing concept of Chipmixer is a nice alternative, but it is rather complicated that you have to import a key manually in your wallet after mixing. I think for the not so skilled user who just wants to pay something anonymously, payout to a specified address is more comfortable.

We plan to integrate some other coins, which is also not very common yet, but before doing so, we wanted to have everything smoothly running with bitcoin and see how our service is regarded by the community. Furthermore we are open to suggestions, so what features do you miss right now?

We would rather keep the amount of coins we hold to ourselves. However as our site states, users are allowed to mix 14 btc at the moment, so our reserve must be at least larger than that.
However I would never recommend mixing this amount at once with any mixer (coming back to the trust issue). Better mix it in small portions and wait until you have them in your wallet before starting the next mix.

Yes, we are working on our marketing strategy at the moment and this is a good option to build trust. Can you elaborate how this is done best? I remember that some other sites did this via bitcointalk.