I agree with entombedtrader.
There are three things to consider.
1. ArcPad has a great form for filling data for users. This kind of functionality can be brought into ArcGIS Mobile and can be custom tailored.
2. ArcGIS Mobile has two options in terms of how it can be used. The out-of-the-box solution where you don't have to write any code. You just follow the instruction using Help, create the project in Project Centre and then you are ready to go.
3. The second option of ArcGIS Mobile is broken into two parts, you can customize the out-of-the-box solution with your own code. This way you can use the existing interface and forms. Or you can create your own application from scratch and build your own interface and forms. This can take a lot of time to build.
In the Mobile Project Center you can actually chose which fields can be display on the form when using the out-of-the-box solution. There is and Edit form and a View form. You will want to modify the Edit form to show only the fields you want your users/operators to modify. The same can be done in code.
All the functionality users/developers want are capable with ArcGIS Mobile, it does take time, skill, patience, and a lot of testing.
There are many good people here on the forums and some decent sample applications where you can learn and understand how to program your own application.
I can say from my experience that using the WPF out-of-the-box solution was good, but most of my computers are slow when running a graphic heavy interface. Whereas my WinForms test applications seem to work much faster, but requires more code and time upfront to complete a project.
One way I look at ArcPad and ArcGIS Mobile, is that ArcPad is made for more GIS knowledgeable users and ArcGIS Mobile is geared more to users with little to no knowledge in GIS. Meaning anyone can pick it up and use. That is how I designed my ArcGIS Mobile application, that anyone should be able to pick it up and perform data collection. Once again, it takes time to develop the application to be user-friendly enough and to meet the use cases (features) that you or your client wants.
Sorry for the long post, but feel free to ask questions.
Regards,
Akhil P.