As someone else has pointed out, if we devote significant amounts of time and energy to maintaining backwards compatibility we'll be saddled with baggage that will prevent the system from evolving. For the limited amount of commercial software that is available, it's the responsibility of the developers to update their solutions to make them more contemporary.
The other consideration is that look-and-feel issues are relatively easy to address once the programmatic limitations are out of the way. While looking at these other operating systems I'm hoping that we gave serious consideration to adopting standards that are commonplace. The GUI doesn't need an update - it needs to be redesigned and rewritten to make sure that code can be easily ported from other platforms.
It's nice to be unique, but not at the expense of ease of use. Look at the simple example of APDF - clearly the biggest uproar is that the application doesn't remotely resemble any of its counterparts. If a GUI element or convention has been adopted by several other operating systems there is likely a good reason for this.
