i've only had my iMac a year and have never used macs before that and i remember that being the only bad thing i used to hear was that they made you have to upgrade all your software whenever they released new OS software - fact or fiction?

if i get the new leopard OS when it comes out will i have to upgrade all my software? (i only use word mac, dreamweaver 8, flash 8, fireworks 8, final cut studio 5.1.4 and photoshop cs and about to get after effects)