Ideally, no, nothing should change across different operating systems. However, we should always check the software against any operating system we think may be used by the client. If the client is only using Windows XP then testing on Windows 2000 probably isn't the best way to get the most accurate results.
Actually, rignt now , I come across a scenario where it's making difference:
I am excuating a Notes script to export the data from Notes R 7 to Word 2003.
When I excuate same in Windows XP (Notes R 7 & Word 2003) it's working fine, however, in Windows 2000 (Notes R 7 & Word 2003) it's going into infinite loop of opening Word. (I stop the procee by kill notes when it had opened 70 MS-Word windows in task-bar).
So, I concluded that it's because of OS; that Notes is not able to recornised whether, the required process is runnig or not