I used to use SI Drums exclusively (when that was all I had)... 
Splitting tracks is time consuming, but not terribly hard... you don't need separate instances, but you do need to use freezing or bouncing... (i.e. wait till you've set your drums in stone). 
I used to solo the kick, freeze it, drag it to a new track, solo the snare, freeze it, drag it to a new track, etc. 
 
Once I got EzDrummer, I never looked back at SI Drums, and now that I have AD2, I'll never look back at any of the others.

But let's not forget SD3, because you can create your own kits with it relatively easily. 

I'm a big Session Drummer fan. I use it much more than Addictive Drumz 2. It's fun and I'm used to it.
 
The SI one is fun too, but I'm faster at getting what I want with Session Drummer.

I have a track template that has 2 instances of SI Drums loaded/tweaked/mixed to a sound I like. I use it a lot. I agree the cymbals are not my go to. But the kick and snares are very good. 

musicroom
I have a track template that has 2 instances of SI Drums loaded/tweaked/mixed to a sound I like. I use it a lot. I agree the cymbals are not my go to. But the kick and snares are very good. 

If you want cymbals, the Zildjian Digital Vault models are off-the-hook excellent. They don't sound "grainy" at all and have a beautiful transparency. Shop around, as prices vary wildly - street price these days seems to be $90, but I've seen it on special for as little as $25.

The SI - Bass is extremely underrated. I used to use Broomstick bass and now use SI-Bass for all my idea-sketching. I'd say about half the time I don't even replace it when it's time to beef the track up. The instruments load fast and are CPU light, so great for quick idea capturing.
 

I want to throw a plug in for the SI Strings as well. Not quite EastWest, but I have been surprised at some of the sounds that can be tweaked from that VSTi. Again, sometimes more than one instance with different settings is always worth checking out if you're seeking richer sounds. They are all fairly light on the resources.

gswitz

but I'm faster at getting what I want with Session Drummer.

I have to also agree with this. When I want quick, basic drums, Session Drummer 3 always gets the call. That's why I got some of the expansion packs for it. Sometimes it stays as the drummer.

I bought a number of expansion packs for SD3, but not all of them are useful.  When I want to load a single drum from a kit (like change kicks in a kit), some of the expansions have flac files instead of wav files.  Loading a flac into a kit results in a very low volume drum.

Just a brief note to all Session Drummer fans. If you see the Andy John's kit on sale (or even if you don't mind paying full price) snag it. It is minimalistic (compared to the AJ kits for other sequencers) but sounds spectacular.
 
Aside from that... I am very much looking forward to having all my input experiments wrapped up so I can begin exploring the wide range of synths (and their patches) that came with Sonar... including the SI stuff.
 
Fancy and complex is good but sometimes so is simple and "does what you need".