Are there degrees of PTSD?

Yes. That is also how the VA rates PTSD is on the severity and how it affects your everyday life.

As a clinical psychologist and a behavioral health officer I can honestly say that a PTSD diagnosis can vary in intensity. Another poster pointed out that the severity of the stress reaction has multiple component parts (i.e, the activating event, the meaning making of why the event occurred, belief structures, and community response). What makes a PTSD diagnosis is whether it impairs the primary areas of functioning (social, occupational, and interpersonal). There are also subtypes of PTSD called delayed expression and dissociative type.
In my experience PTSD is deeply cognitive and emotional which adds another level in that there are some that have been diagnosed and rely on thoughts and problem solving to manage the symptoms. On the other hand some who live with this diagnosis have learned to shut out or off all emotional responses, consequently making them emotionally volatile when triggered.
Treatments vary in intensity as well. There are four primary treatments modalities Prolonged Exposure Therapy (PE), Cognitive Processing Therapy (CPT), Eye Movement Desensitization Reprocessing (EMDR), and Acceptance and Commitment Therapy (ACT). PE is the most intense treatment and extremely challenging for an emotionally constricted and cognitively rigid individual. CPT involves a good amount of work outside the therapy office and focuses on belief structures and meaning making. EMDR involved bilateral eye movements which allows the brain to reprocess the traumatic memory so the individual can heal and let the event be a memory. EMDR can be very effective for MST's and multiple traumas. ACT, said as a word, is a values driven cognitive behavioral therapy that primarily focuses on moving towards post traumatic growth. All modalities are evidenced based and effective for resolving a diagnosis of PTSD. The challenge lies with combating the driving force of the diagnosis, AVOIDANCE. The brain is a wonderful problem solver and when dealing with pain and self preservation we avoid things that are unpleasant. Consequently, the power of the traumatic event overloads the fear response and creates a state of hyper alertness so the system and the individual are ready to fight or run from any real or perceived threat. The avoidance works in the short term and then stops working after several year (7-10yrs in my experience). The individual is now living with PTSD and has avoided people, places, memories, emotions, and new experiences so much so that their functioning becomes impaired.
Great question and I am happy to see some many responses that point towards treatment and getting help, it works (IMHO) to reduce the stigma of getting help and opens the door to those who may otherwise suffer unnecessarily.

Yes, they currently are using four stages of ptsd albeit there are additional degrees but the va is only using 4 at this time.