You can now download and install the official InfoPath SP1.  It is part of the Office 2003 SP1 download.

More details: http://office.microsoft.com/officeupdate/ .  English SP1 download is here.

Please pay special attention to the following if you have installed the InfoPath 2003 SP1 Preview:

InfoPath 2003 SP1 Preview and Office 2003 SP1

If you previously installed the InfoPath 2003 SP1 Preview, you should uninstall the InfoPath 2003 SP1 Preview prior to installing Office 2003 SP1. You will need your original InfoPath 2003 product CD to upgrade to the final version of InfoPath 2003 SP1. For more information, see the Microsoft Knowledge Base article (873040): Information to consider before you apply Office 2003 Service Pack 1 to a computer that has the InfoPath 2003 Service Pack 1 Preview installed.

I have been playing with SP1 for quite some time and it includes some really nice features, there are 3 features that I realy love.
a) .Net programability support
b) Tablet PC enhancements
c) Digital signatures support