I am gearing up to introduce CMMI to my company. Up until yesterday, I was convinced that I should select CMMI-DEV +IPPD using the Continuous strategy. I just read recently another train of thought that indicated for software development improvements only, w should use the Staged strategy and add RM process area to it.
If I choose continuous, will it create more difficulty for me when I begin improving other processes? Is it difficult to match capability levels to maturity levels? I just don't want to do extra work and waste my companies time.
There is no "right" answer for which representation you should choose. I primarily work with clients who select the "staged" representation (which results in a "maturity level"). But there are numerous examples of companies that choose the continuous representation (resulting in one or more capability levels by process area).
The decision to choose one or the other depends on the goals of the organization. If you want to work on improving a large "swath" of your organization - from project management to requirements to engineering - the staged representation is appropriate. If you need to achieve a maturity level of CMMI (say ML2 or ML3) then staged is also appropriate. If you desire to pick and choose amongst improvements, say, only work on metrics now, and requirements later, then the continuous representation is appropriate.
If you achieve Capability Level Two in all of the Maturity Level Two process areas, then "conversion" from a set of capability levels to a single maturity level is simple.
I see the staged representation as a "fork-lift" for bringining a software organization up to a higher level of performance. I see the continuous representation as a jack (like the one for your car) that raises performance for one or more parts of your organization.
The downside of staged is that the scope is large and is quite a bit of work. The downside of continuous is that you'll have processes in your organization performing at all different levels and interfaces between groups will be difficult.
Oh, but the way IPPD is optional . . it's not that it's bad, if you have time it's a great set of practices, but it's an "addition" to the model and is not required.