When comparing tools against Quality Center you should start by assessing how they (the other tools) stack up to QC's functionality. "HP Quality Center has several modules—requirements management, release and cycle management, test plan, test lab, defects management, and dashboard reporting—that are seamlessly integrated to allow for the smooth flow of information across testing stages." more of the write found here: http://h20195.www2.hp.com/V2/GetPDF.aspx/4AA0-9587ENW.pdf
So it would be best if when providing the responses above, that the contributor make the connections between the suggested replacement tool to QC, for example state that "your suggestion" has a test plan, test lab and defects management section but not the others, etc.
I have been a long time user of QC, and I would be very interested in some hard facts/findings of how another tool can perform just like or better than QC currently does. I would have to say that if anyone has in depth knowledge of one of the tools stated above AND they have also used QC for more than 1 yr then they should give their "detailed" Pros & Cons on the subject. This way more of us that are used to QC and find ourselves moving to a company that does not have/want QC can feel confident they can provide the same level of functionality of QC in some other tool.
Maybe it should be the actual Tool creator who should take the time to tell us all how they stand up next to QC's functionality.
Just my professional input.