When adding a virtual instrument today—two years or more after going to X1!—I realized that there is an SI-Drum Kit (in addition to Session Drummer 3 and all the drum libraries I've added).  How did I never notice this before?
 
The cymbals are a little trashy and short for my personal style, and I am not wild about the toms, but I would absolutely use some of the kicks and snares.  For some people and styles of music, there would be lots of good sounds in here, especially with judicious processing.  Basically, more drum sounds for free!
 
That's one impressive thing about Sonar: it comes bundled with a LOT of stuff.

Hallo, Mighty Konrad.
 
I think the SI drums came before Session Drummer 1 & 2, as part of the S.I. bundle - S.I. Strings, S.I. Drums and S.I. Electric Piano.
 
I think the Drums were pretty good for their time, but agree that some of the snares and kicks could still be useful.  Pre-EZ2 release, I would now wax lyrical about Toontrack, but nuff said.  I am thinking of updating to Add Drums2.
 
I still think the SI strings and Electric Piano can hold their weight..
 
I recently opened an old project (Fusion kind of track) with S.I. Electric Piano in, and spent ages trying to replace it with Lounge Lizard (great E.P. vsti, IMO), until I realised that all I was trying to do was make Lounge Lizard sound like the original track.  Sometimes these synths just sit nicely in a mix.
 
Hope all is well with you, Mighty K.
 
Jonathan.

The Studio Instruments are probably the most underrated synths around. They are simple and quick. Yet can sound good. Will they compete with Dimension Pro or Kontakt? No, but for quick work they can't be beat! 

Session Drummer predates all the sfz engine synths including the SI series and Session Drummer 2 and 3. It was an MFX plug-in used to create MIDI sequences. Years later (2006), Session Drummer 2 the sfz based drum synth was introduced with the SI series coming a year or so after it.

I am very happy with the SI-Elec Piano and use it a lot.  I have used the SI-Bass many times.  Now I that have Scarbee Jay Bass, P-Bass, and Rickenbacker as well as Craig's excellent Gibson 5-string, I don't use SI-Bass much, but there is nothing wrong with it.  To me, the default program sounds like a good Precision Bass recorded DI.

konradh
I am very happy with the SI-Elec Piano and use it a lot.  I have used the SI-Bass many times.  Now I that have Scarbee Jay Bass, P-Bass, and Rickenbacker as well as Craig's excellent Gibson 5-string, I don't use SI-Bass much, but there is nothing wrong with it.  To me, the default program sounds like a good Precision Bass recorded DI.

Yeah, how could I forget the SI Bass.  I still use it when writing, and sometimes it stays there, even though I have a PJ and J bass siting in the corner.
 
 

Just be aware that, to the best of my knowledge, it seems you cannot route kit pieces within SI-Drums to separate audio outputs, like you can in other drum synths.  (there is another thread within the past week about splitting SI-Drums).
 
So, I suppose you would need a separate instance for each kit piece to accomplish separate control of each kit piece.
 
Just be aware of that, (if I recall correctly from the other thread - I don't happen to use SI-Drums)
 
Bob Bone
 

Aren't they 32 bit? It was good software but that's what put me off them in the end. Call me fussy.

There are 32bit versions of the SI plug-ins but 64bit versions install with 64bit SONAR.

I stand corrected thanks...