How do PCB vias affect signal quality?
I'm a novice when it comes to higher speed signals, but it just so happens I was researching signal integrity when you asked the question. One source I am referencing is Right the First Time by Lee Ritchey. You will want to check out chapter 25, Right Angle Bends and Vias: Potential Sources of Reflections and Other Problems.

I don't believe the vias will cause any problems in your design. Here is an excerpt from the source:


  Vias, when used in traces, are capacitive, not inductive. The capacitance value of a via is small compared to the capacitance of a trace (3.5pF/inch for 50Ω). In general, vias are not visible to signals with edge rates slower than 0.3 ns.


The chapter goes on to discuss reflections due to PCB layer impedance mismatches, however this appears to be a case when manufacturing tolerances are not met.