Power Sun is a good MVB, though in the past there has been some issues with the bulb. Mainly it looked like some of their bulbs were putting out too much UVB and some bearded dragons were affected negatively. It is my understanding that this issue has been corrected. I don't personally use MVB, however I am thinking of trying a Power Sun in future now that I've finally found a store near me that carries them. It is up to you. If you notice any behaviors similar to what he is experiencing right now, ie eyes closed while basking, hiding from the light, etc. Then shut off the Power Sun and contact the company.
As I've said (so as to not scare you off of them) this issue was a few years ago. I believe there is a sticky on it in the enclosure section if you'd like to read more. As far as I know, it has been corrected.
The shaking is not good. Beardies do not shiver when they're cold, and shaking is often times a first sign of MBD. When is your reptiSun due to arrive?
Are you currently dusting his food with calcium? If so, how much and how often?