New Plug-Ins... Do they usually improve your workflow/sound?

Just a casual question to the community. How often does buying a new plug-in actually improve your workflow/sound? And if it does, how quickly does that effect begin to quickly taper off, where new plug-ins after already having good plug-ins end up sitting on the shelf after a few uses.

In all honesty, much like many others, I've bought into hype when I was a beginner, but it does seem that even the more experienced tend to have the same habit to see something new and go, "oh look, shiny!".

I didn't even buy the Pro-Q4, even though the updates look nice, and it's cool to see saturation models built into it. The menu to mix between tracks and quickly see masking is an awesome addition too. The added control over dynamic is also nice. But... I don't see any of this actually making my music sound "better".

How do yall' feel about this? And for those that did buy Pro-Q4, without over hyping it; do you find it improving your workflow/sound to a greater degree?