A CLEAN INSTALL is always the recommended way to go anyhow.. ESPECIALLY when installing interim daily builds.. I still say it's a waste of time to download them but if you must than please (to avoid a bunch of unwanted problems) do a clean install..
It upgraded from build 7137 OK (since reverted back to 7137 due to other reasons) but upgrade went fine.
In general a clean install is actually better but with so many interim builds it might be better to actually upgrade and wait until RTM for a clean install.
This will depend on the amount of applications you've got installed plus their upgrades and fixes -- for some people re-installing all these every so often can be a real pain so I'd only go for a Clean install if you don't plan on doing many more "interim" installs.
Note that if you have some products like Photoshop CS4 which require activataion then you might find that they will stop working after so many activations -- with CS4 you can actually transfer activation which allows you to re-activate it again - you don't have to have a target machine immediately available to do this - the licensing server remembers it. With other products you might not be so lucky.
With an Upgrade you shouldn't normally have to re-activate your products again .
As far as upgrade from earlier builds goes :
Not tested this but if it upgraded from 7137 it *should* also upgrade from earlier versions like 7100.
RC keys work as well.