Pros
I started with VHB as a Civil Engineer coming out of college. After 6 years, I was convinced that CE was not a good fit for me, and I wanted to change careers into IT. VHB supported me fully in this process, allowing me to change jobs into an open helpdesk position and provided great support and training where needed. That was 5 years ago now, and I have been able to grow my IT career constantly throughout these years. It seems like most companies out there pay some sort of lip service to the idea of professional development. But, in my experience, VHB has really stepped up and delivered for me at every turn. I will say that I'm a highly self-motivated person and that I've taken a lot of initiative along the way. In every case, VHB has matched my effort and initiative with opportunities and advancement. I really couldn't ask for more than that.
Cons
While at the company level VHB is great, the nature of an engineering/professional services firm is that an employee's experience is going to vary widely depending on the team with which they work. Over my 10+ years at VHB, I've worked with many different teams. Some of those teams were great and others were... not great. For anyone considering a career at VHB (or any other similar firm), I think you should make an effort to understand the team with which you would be working and try your best to discern any potential conflicts of personality or expectation. It doesn't matter how "great" the company is if your direct manager is the worst.