Hi Stilgar,
By .NET convention arguments have lower case names and properties upper-case, so it is in paractice easy to tell the difference, at least when using idiomatic .NET libraries (which can, of course, be written i F#)
We trialled several versions of this syntax internally last year. The general feeling was that the simplicity and regularity of allowing both named properties and named arguments as labelled parameters was best for F#. It was in part inspired by named-argument syntax in languages such as Boo.
Kind regards
Don
P.S. In the CTP release of F#, hovering over the names "Visible" etc. will give a hover tip indicating the resolution of the name. Just wait for Brian's screen shots :-)