Few would agree. Its admirers seem to be, well, MS-Windows users, since WP 9 is pretty much the Win32 version running in a WINE environment, with RAM bloat, stability problems, and other glitches (including DOS drive letters in file dialogues!) that are routine on MS-Windows but not Linux.
Very likely, WP 9 introduced some feature-set attractions, but needing to run emulation code with performance and stability problems seems a poor trade-off. I consider 8.1 vastly preferable.
My best guess: Doing a Winelib version allowed Corel to leverage its existing Win32 codebase, write a minimum amount of new code, shorten development time, reduce costs, and keep the effort in-house rather than having to hire SD Corp again.
I hear that you can substitute an improved version of Corel's fork of the WINE emulation code, which for now is maintained by Michael Torrie, at http://students.cs.byu.edu/~torriem/, with other possibly useful pages at http://panopticon.csustan.edu/thood/corel-wp9.txt and http://members.chello.at/hrdisk/corelwine.html.
I can't guarantee the truth of this account, but I've heard claims that Corel deferred submission of its patches to the WINE Project development team so long that they could no longer be merged when they arrived, leading to inadvertent creation of a separate development fork, dubbed "Corelwine". This seems to be the codebase that Torrie maintains, separately from the WINE Project's flagship codebase.
There are also numerous updates to WP9 / WP Office 2000 inside ftp://ftp.corel.com/pub/linux/Office2000/updates/ and ftp://ftp.corel.com/pub/linux/Graphics9/updates/. Among those updates, the revised WP Office 2000 installer available there is essential for most modern Linux distributions to make the Fontastic font server install correctly. Note that you need at least one printer configured before installation.
It's available for US $49 from Surplus Computers of Santa Clara, California at http://www.surpluscomputers.com/. EMS Professional Software and Consulting, http://www.emsps.com/oldtools/wp.htm, has the Deluxe Edition (inquire for pricing). Both editions (Standard and Deluxe) of WP Office 2000 for Linux are frequently offered on eBay.