I’ve tried every comic viewer on my windows tablet, and Sumatra works the best. My tablet has a slow atom CPU and only 2gb RAM, so Sumatra’s simple design and low system requirements make it ideal.
The only feature missing is an easy way to open up the next comic issue when I finish the one I’m reading. Buttons on the top toolbar to skip to the previous or next file in the current directory would do the job nicely. If you want to get fancy, a file skip gesture like two-finger swipe would be even better for those of us using a tablet.