Well the new imposition in Equios is somewhat like metrix. I think the ganging option for example bears a lot of similarities to Metrix. At this point I can't see that Metrix can do much more (if at all) that Equios can with the execption of calculating price for a print job. The reason Metrix was introduced by Screen was because you couldn't do everything with Flatworker. The definite up side of Equios is that the imposition software is inside the client and in all clients without any restrictions on either the size of imposition or the user amount.
To me Equios was a huge jump in usability and now that it is in version 3 the imposition has become even more flexible. Depending on the size of your organization the limitless user count can be a big benefit financially. Not to mention the fact that Equios is still an update to Trueflow.