There are two Problems:
The scale is not respected.
The html5 number input type doesn't allow decimal points by default (needs step attribute), even in US locale, in Chrome. (oops)
When setting the scale-constraints for a BigDecimal higher then 3 it is not reflected in the views.
It configures the scale value correctly in the DB-Scheme. Even the create-view works correct. Correct value is persisted in DB.
But after that, only the first 3 decimal places are shown. Even on the edit page everything more then the 3 decimal places are omitted.
The result is that you loose information!
Whats adds up to this problem is that when you use html5 capable browsers like chrome or opera you won't
be able to type in any decimal places. They interpret the <input type="number" as an Integer value. (As mentioned in 1) it needs the step attribute)
The behaviour is double confirmed on the mailing list http://grails.1312388.n4.nabble.com/Grails-2-0-0-RC1-BigDecimals-and-Scaffolding-td3943888.html + I'll attach a example app scaffolding the following simple domain class.