Recce,
I have no concerns, but then, I haven't yet implemented it!
My company intends to go PPWR this year, so merely came accross it when researching Upfront and customisation.
Naturally, with it being a third party application, there will always be concerns about conflicts with Cognos, other applications and your OS. However, given that it has been recently upgraded for version 7 and that special licencing is available for Cognos employees, there is obviously skill and interest behind it.
Perhaps another member of the list can offer a testimonial? An old hand like Dave Griffin may have tested it (Dave - no insult intended!)
lex