Target display mode is a nice feature. However assume you are lucky to have both iMac and MBP
such that the MBP is your main and strong computer and you keep the imac for cases the MBP is not around.
They you'd want the iMac to behave like a standard 27" LED display. TDM does almost that, except:
1. The keyboard and mouse still belongs to the iMac - you cannot use them with the MBP unless repairing or
other annoying and "dangerous" steps.
2. The MBP in clampshell mode stops the TDM again, not you want.
I'd be great if you could set a special preference pane for TDM where you can set all these rules so it
does what you want.