I use the CMM in my work. The CMM/CMMI is a wonderful collection of key process areas. Every product development environment can use many of the key process areas to improve their work. The keyword in that sentence is *many*, not all.
When companies aim for a particular level of the CMM/CMMI, they do themselves a disservice. By aiming for a level, they say that all the key process areas at one level are equally important. But what's most important is not the level, but the mastery of the appropriate key process areas.
For example, a key process area in Level 3 is risk management. As you know, risk management is necessary for successful project management. In fact, I could argue that many organizations at Level 1 have mastered a form risk management, albeit in a people- and company-destructive way.
Here's hypothetical example: A company with great project management processes including risk management whose project managers and technical staff are savvy enough to recognize that their lifecycle and practices need to change on each project. They have an incredible test group. They don't perform formal QA, their requirements are bullets in email (a step up from napkins), they don't track anything other than defects. They're somewhere between level 2 and 3.
Here's what matters: they work. Their projects work. They ship product on time. The customers, the compay, and the technical staff are happy. Their customers don't find egregious defects. Their process works. They have mastered the few process areas they need now. As they grow, especially as they bring more people into product development, they will need to reconsider how they define and manage requirements, what they measure, and how the developers review their work. They will increase their mastery of the next process areas that matter.
When you plan and perform process improvement, especially if you don't have a contractual need to show a certain level, work for mastery. Define which key process areas are strategically important to you *now*, and master those.
Levels are like grades – they show some part of what you know. But what's most important is how you apply the knowledge behind those grades – the mastery.