Well, perfect result.
But I was confused by the grub menu choices.
If you can detail where the confusion is then maybe the explanations can be reworded to make things clearer.
I chose the first entry, since I had already installed grub. But I got no login screen, just straight to boot.
Sorry, I don't understand what you mean ..... did you get a Grub screen to select the OSs on the USB?
I couldn't make sense of any of the grub seections, but like I said in my previous post I am a bit dense.
It was the same with the repo version but I always chose to install a fresh grub.
As above ...... if you can tell me where the confusion lies then maybe it can be made clearer.
Great job, I'll keep playing.
2nd try:
Chose all boot options, chose 3rd grub choice to reinstall grub
hmmm.....again no boot menu. Straight to desktop. 
havin' fun, hth. 
btw...this is on my 32bit partition
The Grub screen and the Desktop login are separate things.
The login is determined by the ISO ...... and in all later ISOs there is no login when running live, it automatically logs into the Guest account.
If you have no boot menu then you cannot choose which OS you wish to boot? .... you mentioned having two previous OSs on the USB drive ..... do you not get the opportunity to boot either of those also?
If you can post again giving details of what is happening at the different times it will be easier to know where the problem lies.
Thanks for testing and reporting back
