Maddineni,
Reps from the responsible companies or users that own the tools may clarify what I've written here. We are writing a purchase order for the "Assignment Editor" from ITDesign, and have investigated the ITROI Excel integration. Also, you may find that the solution offered by CA is in fact the exact same solution provided by their partners. ITDesign, ITROI and Rego, amongst others, are all CA partners.
The ITROI Excel integration is one that resides in an Excel file that you provide to users. If users are not part of your IT CA PPM support team, you're likely going to configure the integration in Excel to allow users to perform a limited set of downloads, that they can then edit, create new and save back to CA PPM. The user needs a copy of the Excel file with the macros installed. Last we checked, once the license was purchased, any number of files could be created with the installed macros and distributed amongst your user base. Macros in Excel include a login capability, which uses the CA PPM login credentials and security/access settings. The tool is capable of downloading about everything from CA PPM - you shouldn't give it out to users without preconfiguring it and locking the configuration in Excel, else users will be able to get into stuff you might not want them getting into. The integration uses your lookups, and it includes data validation when saving back to CA PPM - it will let you know if a record's change was not saved and why.
The ITDesign "Assignment Editor" is a series of screens that are delivered by the CA PPM UI through portlets to your users - it is not installed on individual machines. As these screens are delivered through CA PPM, it uses CA PPM's login credentials and user security settings as defined in CA PPM. Unlike the ITROI Excel tool, this "Assignment Editor" is very focused on one particular topic/data set. As its specifically designed to do one thing, you may fined it a more tailored solution that the ITROI - 'download/upload anything and everything' tool. Both have their place, and I'd like to have both, for supporting different purposes.
The two tools are using CA PPMs XOG (XML Open Gateway) capability, so there are no data integrity issues. However, one caveat - neither tool locks records while one is working on them.
CA will likely direct you to the partners for demos, details, questions - this has been our experience.
Give 'em a call. Its been a few months since I've met with any of these companies - please contact them directly to get the latest information. Apologies to any of the three partners where my words are out of date!