Drives supporting CD-MRW include defect management and address compatibility issues by specifying the exact UDF format for use on CD-RW discs. This ensures a standard for sharing discs between computers. Looking forward, newer operating systems versions (such as MS Windows XP) will have the drivers embedded to support the new writing format.
Other key features include:

Formatting in the background
Writing to a CD-RW disc using packet writing requires that the disc be formatted first; this has taken a very long time in the past. With CD-MRW, formatting is now automated. When a disc is inserted into the CD-MRW drive, a transparent background format will be carried out. Data can even be written to CD-RW during the actual formatting process, eliminating wait time altogether.

CD-RW discs can be ejected at any time
Now, similar to a floppy disk, CD-RW media can be ejected at any time, even before the formatting process is complete. Once the disc is reinserted into the recorder, formatting simply continues where it left off.

Logical 2K addressing
Conventional packet-writing methods process data in blocks of 64K. In contrast, Mount Rainier utilizes a block size of 2K, thus making better use of disc space and reducing the time required to copy files.

Physical fault management by the drive
Unlike UDF version 1.50, where defect management relied on software, CD-MRW ensures that defect management is handled through hardware (directly by the recorder itself). This frees up system memory and processing power, for system critical functions and multitasking.

Note: InCD supports Mount Rainier;
version 3.24 or above is required.