I agree, this is an excellent article - I could have done with it before I took MCTS/MCITP in the last couple of months (although I did pass).
I think that the MCTS Self-Paced Training Kit (Exam 70-448): Microsoft SQL Server 2008 - Business Intelligence Development and Maintenance book is worth mentioning though. Like you I found MCITP easier because I had some experience of all three BI strands. The MCTS exam is more 'nuts and bolts', e.g. knowing the syntax of dtutil. This book is geared to the exam, and also has MeasureUp self-test exam questions included on a CD. It also has an excellent chapter on Data Mining (one area I don't yet use in my current job), which in my opinion is enough to cover the DM subject matter for both exams. I would certainly not got through MCTS without it, despite 6 years of MS BI experience.
I'd also like to mention (no, I don't work for Microsoft!) the book Reporting Services 2008 Step-by-step. I have more SSRS experience than SSIS/SSAS, but this still taught me the extra 10% I needed, particularly as I am a developer so my administration skills and experience are at a lower level.
I used Kaplan's self-test software (mentioned in the article) to prepare for the MCITP - there appears still to be nothing offered by Microsoft to prepare you. The course 50399A is constantly promised but deadlines come and go without it being published. The self-test was very useful, and did help me answer several questions, particularly on the infrastructure side. My personal belief though is that it was too infrastructure biased and also includes a lot of pure SQL Server-related questions compared with the exam, but that may be just my experience.
Last point - I use SSIS now more than the other two, yet performed worst on the SSIS sections. I think the moral is you have got to know SSIS in detail, particularly what each task/component does, and the bits that maybe you don't use day-to-day like logging and checkpoints. It's frustrating that features many people discredit (such as SSIS logging and SSAS Proactive Caching) and hence may not feature in your day-to-day work you still need to know well to pass!