Sonar X3 is a fine development of the software.
I think that the key point here, though, is that the price structure has changed quite a bit since Sonar 7 and 8. At this point, the Producer edition's added value, versus Studio, is entirely in bundled plugins. The extra cost to upgrade to X3 Producer from X2 Producer still represents a decent price for that bundle, if it offers you something of value - a few of the ProChannel effects and some of the VST instruments are certainly useful, although most of these are accessible even if an X2 Producer user upgrades to X3 Studio. Both XLN and Celemony seem to be stand-up companies committed to ensuring that no-one falls through the cracks if they already own the software, etc.
Nonetheless, it's a fact that the price structure has changed, such that the Studio edition offers power in the core software comparable to what in the old days was available only in the Producer edition.
I really wonder why Cakewalk hasn't marketed this as a drastic price drop in the Producer edition, and introduced a new "suite" edition above the Producer edition. I think that is a missed opportunity for them.
I also think that for those on the Producer upgrade path, the gradual erosion of its superiority in the core software means that Cakewalk risks having them hop down to Studio. What then happens when Producer once more gains the killer feature absent in Studio? More griping I suppose...