Hi Paul,
Just spotted your question. I have been using a Daystar Quark Chromosphere for a year now and had no reliability issues at all with it.
It is a sturdy piece of kit although the bottom of the quark that sits in the diagonal can become loose from time to time but that is just a matter of screwing it in.
The main issue I find is dialling in the Quark to get the best image of the Sun possible. I understand that each Quark is ‘unique’ in this respect. You will see that there is a tuning knob at the front of the Quark which can be set at the 12 o’clock position and then adjusted +/- 5 clicks either side. Adjusting this tuning knob by one click either clockwise or anti clockwise adjusts the wavelength of H-alpha by 0.1 angstrom and allows the user to get the best view possible.
For instance, adjusting mine anti clockwise from 12 o’clock can remove any prominences from view, whereas adjusting clockwise can improve the view of the chromosphere and prominences. I find mine offers the best viewing one click clockwise of 12 o’clock. If you do make the purchase (or done so already) spending the time to find the sweet spot is recommended. Usually attaching a camera and capturing 500 frames on each setting then processing each run will allow you to assess which offers the best setting for what you wish to observe.
I predominantly use mine with a William Optics Z61and a ZWO ASI174MM camera. For safety reasons I very rarely view with an eyepiece and almost always use it in conjunction with my laptop (you never know if something will go wrong or fall off!). I have also used it with a WO Z103ED with no issues at all. In regard to a power supply, I use a solar powered battery power bank (typically used for charging mobile phones) which works well. Given the Sun is out when I am observing/imaging it is also a reliable source of power!
Overall, the Quark Chromosphere has been a great addition to my observing kit especially in the summer when the nights are short for DSO imaging and it also allows me the flexibility to use either my Z61 for wider views of the Sun or more detailed shots using the Z103.
I would recommend it if you are considering moving away from the PST and want the flexibility of using a wider aperture scope.
John