PowerShell accelerators

PowerShell is object oriented and based on the .NET framework. This implies that there are no types, only classes, but to make the daily life to the PowerShell user Microsoft has added some accelerators to PowerShell. So instead of being forced to go the long way and write [System.Management.Automation.PSObject] you can settle with [psobject].

To get a list of accelerators through the Assembly class you can use the statement
[psobject].Assembly.GetType('System.Management.Automation.TypeAccelerators',$true,$true)::Get
and on my current workstation with PowerShell 4.0 there are 80 accelerators.
The method GetType() has three implementations, and the one with three parameters is used to get the most stable and predictable invocation.
The class TypeAccelerators is private, but accessed through a PSObject object.

Some accelerators are named in lower-case and other in mixed casing (CamelCase). Generally I prefer to use the casing that the accelerator has in the definition.

I have not seen any indications on a performance hit when using accelerators. And as the code is so much more readable with accelerators I go with them where it is possible.
When it is not possible I use the full class name, e.g. "System.Data.SqlClient.SqlConnection".

It is possible to create custom accelerators like an accelerator for accelerators:
[psobject].Assembly.GetType('System.Management.Automation.TypeAccelerators')::Add('accelerators',[psobject].Assembly.GetType('System.Management.Automation.TypeAccelerators',$true,$true))
The accelerator is then available like any other accelerator:
[accelerators]::Get
This accelerator is part of some PowerShell extensions.
Personally I prefer to name custom accelerator in lower-case.

Reference

RAVN Systems: PowerShell Type Accelerators – shortcuts to .NET classes