That information is not entirely correct.
One needs 824 only if the 140 is approved with 485 option. If it is with CP option you can go straight to CP.
Currenly CP is taking from 6 to 8 months only from the date of 140 approval. In my case I got my 140 approved on December 12 th of 2002 and my CP interview was on 21 May 2003 (Chennai) and I got my card on June 22 nd.
I know some of my friends who have the same 140 approval dateas mine but opted for 485, still waiting and may need to wait for another year or so.
Regarding portability, 485 may give you an option to change jobs after 180 days but still you need to worry about finding a similar job etc and wading through paper work and continue the frustrating waiting. With CP you may be able to get the card in this time frame!
If you are not sure about holding on to the job for 6 to 8 months CP is not a good option.
dmn