I've posted a poll to get a feel for the PowerShell community's preference on this. Compiled Cmdlets offer much better performance than the equivalent PowerShell advanced function, which can be a very valuable thing if you need to process large sets of data in your scripts. The other side of that coin is that in order to make changes or review the code of a Cmdlet, you need to start working with C# (and likely Visual Studio as well.) Which do you feel is more important when downloading a module: performance, or sticking with familiar PowerShell code?
The poll is over on my blog.