As I come from a print design background this kind of stuff (variable unpredictable spacing) drives me crazy!
As Daniel mentions all browsers often render text, with the same settings, differently. Unless it is Headline~Display text I don't bother - along with all the other inconsistencies in the modern web - it's just one more thing.
For Headline~Display text I use a span set-up for the space itself. It can be tedious - especially if You are trying to please all the major browsers.
Note: I have not done this in Hype as if I get any grief with any headline text I create separate blocks for the offending portion(s). This is what I use for Dreamweaver...
<span style="word-spacing: .25em;"> </span>
You can of course create a class for your span, but I find they all usually need a unique adjustment.
Below: six custom settings for the spacing as rendered in Safari. Chrome and Firefox look slightly different so the settings are a compromise; but it is far better than the default word spacing. What really threw a wrench into the works were the bullet point separators plus the use of the ampersand.
Commercial • Residential • Consulting & Design - should be simple - right? ;->