Your side effect is super cool, specially if you imagine that even light would be frozen in time. People in this thread keep choosing side effects that would ruin the super power but this one would be a problem but still worth using the power. With some practice you might even overcome some of thrle drawbacks.
Now I want a super hero with this power and side effect
What's funny is that the most obvious side effect to this is the most realistic: molecular manipulation in this way causes an incredible build-up of energy that either expresses as kinetic or thermal, depending, and almost always exponentially explosive from the moment you turn time back "on"... to say nothing of the disastrous effects at the fringes for such time-stop powers...
tl;dr: The Flash would've incinerated the entire planet long before he discovered how to keep from glassing it simply by practicing his powers.
Also photons cease to exist once you move into their space, there would be no light to enter your eyes attoseconds after stopping time, meaning you would be blind.