The config spec in our project is generated and included as file in hudson. We have different branches for different VOBs and some VOBs are referenced with labels. It's tricky to enter all branches and labels in hudson to have right chagelog (lshistory). e.g.:
"load vob1\source1" with branch "min.10"
"load vob2\source2" with branch "min.10.01"
"load vob2\source3" with branch "min.10.02"
"load vob3\source1" with branch "min.10.05"

So if we enter branches: min.10, min.10.01, min.10.02, min.10.05 and some of them are not there for some VOBs we will have errors:

[hudson.min.10] $ cleartool lshistory -all -since 3-feb-11.12:01:38utc+0000 -fmt '\"%Nd\" \"%u\" \"%En\" \"%Vn\" \"%e\" \"%o\" \n%c\n' -branch brtype:min.10 -nco vob1\source1 vob2\source2 vob2\source3 vob3\source1
cleartool: Error: Branch type not found: "min.10".
cleartool: Error: Branch type not found: "min.10".
cleartool: Error: Branch type not found: "min.10".

[hudson.min.10] $ cleartool lshistory -all -since 3-feb-11.12:01:38utc+0000 -fmt '\"%Nd\" \"%u\" \"%En\" \"%Vn\" \"%e\" \"%o\" \n%c\n' -branch brtype:min.10.01 -nco vob1\source1 vob2\source2 vob2\source3 vob3\source1
cleartool: Error: Branch type not found: "min.10.01".
cleartool: Error: Branch type not found: "min.10.01".
cleartool: Error: Branch type not found: "min.10.01".

[hudson.min.10] $ cleartool lshistory -all -since 3-feb-11.12:01:38utc+0000 -fmt '\"%Nd\" \"%u\" \"%En\" \"%Vn\" \"%e\" \"%o\" \n%c\n' -branch brtype:min.10.02 -nco vob1\source1 vob2\source2 vob2\source3 vob3\source1
cleartool: Error: Branch type not found: "min.10.02".
cleartool: Error: Branch type not found: "min.10.02".
cleartool: Error: Branch type not found: "min.10.02".

[hudson.min.10] $ cleartool lshistory -all -since 3-feb-11.12:01:38utc+0000 -fmt '\"%Nd\" \"%u\" \"%En\" \"%Vn\" \"%e\" \"%o\" \n%c\n' -branch brtype:min.10.03 -nco vob1\source1 vob2\source2 vob2\source3 vob3\source1
cleartool: Error: Branch type not found: "min.10.03".
cleartool: Error: Branch type not found: "min.10.03".
cleartool: Error: Branch type not found: "min.10.03".
...

So it's more complicated if some VOBs should be used with labels and the config spec file is dynamically changeable. Because of this we use snapshot views and use the updt file as changelog:
Log has been written to "D:\Views\hudson.min.10\update.2011-02-03T131647+0100.updt".