gamera~. Yep, it is a good idea to know Objective-C 1.0 as it now known before doing Objective-C 2.0. This is not upon some perverse form of initiation into the programming language, but rather an understanding of what the properties in 2.0 and how the garbage collector runs.
If you say get a job in developing Cocoa apps, you will run across code written before Leopard. In this case, you will need a thorough understanding of how the NSAutoreleasePool works and how the retain-release mechanism functions. These are not difficult concepts, but they confuse programmers new to Objective-C, especially from languages like C# or Java.
Also, when writing apps on Leopard, developers may choose to ignore the garbage collector. They don't ignore it as they are trying to prove they don't need hand-holding, but rather the fact that they cannot rely on when the garbage collector will run. This can cause serious issues when performing rendering, e.g. Final Cut Pro. The developers want in this case to be in charge of allocating the memory and deallocating it themselves.