If you say SharePoint 2003, my respected colleague down the hall from me, Mike Fitzmaurice, won't be very happy. You see, SharePoint 2003 really doesn't make sense; it doesn't mean anything. Tell that to the authors of Microsoft SharePoint 2003 Unleashed - incidentally, a good book.
When people use the word "SharePoint" in a standalone fashion, they usually refer to Microsoft SharePoint Products and Technologies - a phrase that is acceptable. Microsoft SharePoint Products and Technologies is the umbrella term for:
1. Microsoft Windows SharePoint Services, sometimes shortened to Windows SharePoint Services or even SharePoint Services or simply WSS.
2. Microsoft Office SharePoint Portal Server, sometimes shortened to SharePoint Portal Server or even Portal Server or simply SPS.
If SharePoint isn't a noun, then what is it? It's an adjective. You can use it when describing something. Proper examples of usage include: SharePoint site, SharePoint expert, SharePoint Web Part, et cetera. You just can't, technically, say "I deployed SharePoint". It doesn't mean anything.
Now... having said all of that, I personally have no problems with the way people use the word SharePoint. At the end of the day, as long as you get your point across, it works. But, my colleage Fitz does get a little peeved :-)... so, the next time you use the word SharePoint, you may want to think about what you're really trying to say.