I use them all the time. The Modulation plug is like having, well, 30 boutique pedals. The 30 modulation preset freebies in the 2017.06 update and the 30 CA-X amps in the 2017.08 update should get that point across.
 
The Wah plug can model a Clyde McCoy/Thomas Organ Vox wah wah pedal with uncanny accuracy, and the envelope followed filter aspect is aces.
 
The Delay does crossfeed, diffusion, and tricks other delays just can't do.
 
The Phase plug-in does phase-based widening that doesn't collapse in mono.
 
The Multiband is fantastic when you want a crossover for multiband processing that doesn't take a lot of CPU. You can also compress the crap out of the top bands when feeding an amp sim to provide the equivalent of a dynamically-driven "rolling back the tone control for a creamier sound" with guitar. You can also treat it as a graphic EQ with user-definable bands in which you can add compression if you want.
 
There are many reverbs that are better than the Sonitus reverb if your only interest is sound quality, but the Sonitus has its own sonic signature that I find useful, particularly in parallel with long delays and as the basic for modeling impulses.
 
I could go on (like how the Surround does cool vibrato and tremolo), but you get the point...how you apply a plug-in matters too.

They're fine plugins, the GUIs make them a bit fiddly to work with IMO. The compressor was the first one I use that had a graphical display of the compression curve. As a novice it was really helpful to visualize what was happening. When they were all that was included in Cakewalk/Sonar (not sure when the were added?) I used them all the time. I don't really use them anymore.

I rarely use the EQ or Compressor these days, but I still make good use of the others - Delay, Gate, Modulator, Phase, Multiband Compressor & the Surround Panner (works GREAT on mono or stereo tracks)

Sonitus reverb is my main choice .

I still have the Gate and Compressor on my vocal tracks because I built them into my usual project template years ago and I've never bothered to change it.

These venerable plugins are a staple on all my projects. I think they are great, and as kzmaier says, low CPU. 

 

rmfegley
They're fine plugins, the GUIs make them a bit fiddly to work with IMO. The compressor was the first one I use that had a graphical display of the compression curve. As a novice it was really helpful to visualize what was happening. When they were all that was included in Cakewalk/Sonar (not sure when the were added?) I used them all the time. I don't really use them anymore.

Yeah, I kind of like the look and feel of parametric EQ, like those on the Channel Strip.
Here,s the thing, being a traditionalist can be good but also very bad because you don't get out of your mindset and I hate to miss out. :)

Anderton
I could go on (like how the Surround does cool vibrato and tremolo), but you get the point.

Please do Sir. :)

I have used the delay on every song I recorded with Sonar. Instead of doing double tracking, I sometimes prefer to use delays on vocals or rap verses.

But as I mentioned below, sometimes you have to spread your wings, to experiment and apart from the RME effects I mentioned, I have really never used other FX outside of what ships with Sonar.

I just don't like the graphical GUI of the EQ, I know this has nothing to do with sound but there is something about dialing a knob, especially when you are used to analog stuff.

Curious, Has there been any updates or changes to this plug in?

Well Hardware EQ's came as both Graphic and then the Parametric so it's the same here. There are plug is of both and many that combine the features like "Q" and low and hi pass filters so pick the one that seems the easiest to dial in the sound you want. My go to EQ is the LP. Easy to add a hi pass. Seems low CPU too.  

 
Yes, love the high functionality packed in a no-nonsense GUI.