I've seen essentially nothing but gripes about Sampletank since I've been on this forum (which has been for years).
 
I have Amplitube from IK Multimedia, and I've now received a crossgrade offer for Sampletank at $200.
 
I've developed a motto over time that I will never, ever, ever, ever buy another compressor.
 
I've recently gotten to that point now with synth and keyboard sounds, since I have Omnisphere, Kontakt, AAS keys, and of course Dimension Pro and Rapture.
 
So I've been thinking I'm now saturated with more keyboard sounds than I could ever use, and they are unbelievably awesome.  So I'm thinking I should never ever buy another set of keys or sample sounds.
 
Is there something special about Sampletank, and at $200 I'm an idiot to pass on it, or is it just an average, outdated set of proprietary samples, with nothing special going for it?
 
Is there anything that anyone could illuminate me on as to why I should be interested in it?
 

If you have SampleTank 2XL or any of the other ST Instruments
(SampleMoog, Miroslav, SonicSynth, SampleTron) and want a better
64 bit interface....then that's the only way you'll get it I'm afraid (right now)
But, is there anything that's going to be better then what you have with
Kontakt or Omnisphere?  Not really...not even in the same ballpark IMO
Sample-wise or otherwise....

But, most believe I'm biased, so take my opinion for what it's worth.

lawajava
I've developed a motto over time that I will never, ever, ever, ever buy another compressor.
 
I've recently gotten to that point now with synth and keyboard sounds, since I have Omnisphere, Kontakt, AAS keys, and of course Dimension Pro and Rapture.
 
So I've been thinking I'm now saturated with more keyboard sounds than I could ever use, and they are unbelievably awesome.  So I'm thinking I should never ever buy another set of keys or sample sounds.
  

 
ST3 doesn't offer anything particularly groundbreaking and the included library contains a lot of bread and butter sounds that will overlap your existing Dim Pro and Kontakt factory libraries. It does have some very nice things, but based on the way you describe your "need" for more sounds, I wouldn't describe it as "compelling" in your case. There are some ST3 reviews over in this thread:
http://forum.cakewalk.com/Why-I-bit-on-Sampletank-3-m3069556.aspx
 
And the pre-order pricing (it was released just over a week ago) was $50 cheaper that that, and given IK's history at some point in the future it will likely be discounted even further.

ST 3 does offer a lot of high quality sounds IMO and comes outfitted with beau coup excellent effects on board.  But if you have Kontakt and the other instruments you named, do you need another sample player?  That I cannot answer.  But I support what Larry said - if you have Sample Moog and Sonic Synth, which obviously you don't or you'd be talking about the upgrade price, you would want ST 3.  I just went through a bunch of my Sample Moog sounds and it's "welcome back, Sample Moog!!!".  I'm very please to have ST 3 on my system.

I don't have it yet (ST3) but now I have found out I can transfer all my old stuff (samplemmog, sampletron, sonic synth , miroslav and all the Esounds stuff I have) I will now probably upgrade, just so I can use all the old stuff again!
 
If you don't have any old stuff, and as you already have Kontakt, I really can't see any reason why you would want to bother - whilst I am sure the new sounds will be pretty good, I can't believe you won't find as good or better sounds in  Kontakt - obviously I have not compared these yet, but I'm going on what other people have reported so far.
Also ST3 is BOUND to be a on Final offer / Group sale / Winter sale / Christmas sale / there's a Y in the day of the week sale any time soon!!!!!
Nigel
 

I concur with several points made by previous posters. I have not yet received my box set.  However, the reasons I went ahead and ordered it were these:
1.  Its 64 bit
2.  It has a larger and finally readable  GUI
3.  It integrates several IKM effects from T-Racks right into ST3.
4.  It can import the other IKM sound libraries (Miraslav, SonicSynth, SampleMoog, SampleTron); I own all of them.
 
To be honest, I have not used ST2.5 in years--primarily because it is just too small to see; I have very bad vision.  I actually like the sounds found in many of the previous IKM synth libraries, but have not used them because of the GUI.  So, I went ahead and purchased ST3 not to get its new sounds so much as to regain access to all of my IKM sound libraries in a usable, readable, 64bit native application.  From what I have read here on these forums, others are not overly impressed by the new ST3 library; I have so many specialty libraries for Kontakt that will probably surpass ST3's core library;  I can live with that (if what others are saying is true), BUT I look forward to finally getting to use all of my IKM toys (libraries) once again in the new GUI.  Hopefully, having this nice GUI with improved visual access with spark some new creativity in me; it will be like getting all the IKM libraires at once (almost like the first time) again.  For $99 (which is what it cost me last month), this is actually an affordable price to pay for me to finally gain visual access to all of the IKM catalog.  
 

Not sure I can add much else to what has already been said.  I'm pleased with my purchase, but then again I don't already own most of the products you listed. I am very pleased to use libraries like Miroslav in a much easier to use interface.

Thanks for the input so far.  Not exactly a resounding sentiment that at a $200 price for a first time buy it's a screaming deal and there's just too much to pass up.
 
I'm both overwhelmed and extremely satisfied with the ones I have, but there's always been a key reason for each the prior purchases because of something they offered that really made it worth it to make the jump.  In this case, I'm presently on the sitting on the sidelines side of the fence, but observing with interest.

Lawajava
If you're not 100% I'd just wait for the inevitable  sale..............
Nigel
 

I bought st3 upgrade for $99 at the presale. I am very happy with the purchase because
1. 64 bit sits with Sonar X3 64 bit nicely
2. tons of new sounds to compliment my komplete 9. There are some sounds that ST3 has but not K9. For Ex, many useful basses and gtr, jazz/pop brass, certain yamaha E Grand, Chinese Gu Zhen, different variety of synths and electronic drum(actually I prefered the synth samples in ST3 over Kontakt 5) 
3. Ease of use, you can quickly put together a track.
4. lots of useful and good sounding effects 
5. Bigger and Better GUI, ex, all 16 tracks in one page, all synth parameter in one page,
6. lots of useful midi drum patterns
 
I am saying ST3 compliments the Komplete 9, not better by any means,but just just different
But for now, I am using the vst2 version. The vst3 has some stuck note issue when using in PRV mode.