What issues normally arise after converting from Windows xp/ Office 2003 to Windows 7/ Office 2007.?

After upgrading from Windows XP/ Office 2003 to Windows 7/ Office 2007, how can I identify any technical issues or what tests can I run to identify any technical issues when using Excell/ Word/ Access etc. The problems im looking for are any problems with buttons, formatting etc. Any advice would be great, Thanks !