Our company is undergoing a pilot to replace cognos cube with MS cube but still retaining upfront and other cognos infrastructure, ie, Powerplay web, upfront, access manager, PPES, and etc. The path of integrating the two products proved to be quite painful, and I'd like to share with you 3 critical issues we ran into. If any of you encounterd, and resolved any of the issues listed here, I'd definitly love to hear from you.

Here is a bit of info related to our environment.
Cube : MS analysis service advanced 2000.
COgnos: 7.1
Cognos PPES and MS Analysis reside on two different 8 CPU box.

1) Unable to reproduce Cognos Time Dimension functionilty.
Cognos Time Dimension is very convenient to use. It allows you to present not only the time dimension, but also any time related function, YTD, MTD, all under time dimension. We couldn't reproduce the same functionality within MS cube, so ended up separating the time related function as calcuted member in another dimension. Personally, I am quite comforable with this design. However, we are facing many critism from the user group since it is not what they are used to. I am curious to know whether this is possibile in MS cube, and how.

2) Performance issue when MS cube is rendered in upfront.
For most cognos newsitems based on MS cubes, performance is acceccptable, and comparable to the ones based on cognos cubes. However, for those with many nested levels, performance through upfront just grind to a halt. The same report based on cognos cube are still performing satisfactorily. The interesting thing is I can see MS cube is performing well when the same drilldown path is excerised through PTS in excel, thereby indicating the issue lies within the interface of the two products, or possibily just Cognos PPES or upfront. This is where I really hoped either vendor would step up and offer some best practice advice in terms of integration configuration, tunning. To my disappintment, there is none.

3) Poor security management.
We intend to use Cognos access manager to manage security set up for MS cubes. To my surprise, the way that Cognos implemented this part of security seems really stupid. (most likely on purpose). Access to MS cube can only be granted to a user, rather than to a user class. This is extreamly disappointing since our user base are in the hundreds.

There are several more less critical issues, but I guess that is enough problems for a day. :-)