I guess everyone IS different.  I like the Cuban and African libraries because they are different and some flavor.
 
Strummed Guitar is out now so it should be included in Komplete 11 when that is released - maybe even a Strummed Guitar Pro for Komplete 11 Ultimate.
 
I do agree that Native Instruments is kinda weak in the guitar libraries.

sharke
I just upgraded from Komplete Ultimate 9 to Ultimate 10 (HD is in the mail) and I feel that for $200 it was well worth it. Session Horns pro  - come on. But not only that, there are 2 or 3 great new synths and some fantastic new effects in there. I'm looking forward to trying out the new EQ's and reverbs. If there's one complaint I have about Komplete is that they should really get rid of some of their more esoteric and specialized libraries and replace them with some more meat and potatoes stuff. For example, get rid of the Cuban and African libraries and replace them with some more guitars (especially acoustic). 

I really love the African library.

sharke
I just upgraded from Komplete Ultimate 9 to Ultimate 10 (HD is in the mail) and I feel that for $200 it was well worth it. Session Horns pro  - come on. But not only that, there are 2 or 3 great new synths and some fantastic new effects in there. I'm looking forward to trying out the new EQ's and reverbs. If there's one complaint I have about Komplete is that they should really get rid of some of their more esoteric and specialized libraries and replace them with some more meat and potatoes stuff. For example, get rid of the Cuban and African libraries and replace them with some more guitars (especially acoustic). 

I really appreciate the different textures (i.e the more esoteric and specialized libraries) available in the Ultimate editions. While I look forward to checking out all the new stuff - the Cuban library was the deciding factor why I'm upgrading from Ultimate 9 to 10. 
 
Except for perhaps creating a real replacement for the discontinued B4 plug-in - Ultimate 10 for my taste seems to have an abundance of meat & potatoes (drums, bass, piano, etc).  As a guitar player I tend to ignore guitar sample libraries so I can't comment on that area but do agree that a good acoustic guitar library wouldn't hurt... 

I've got Komplete 9, (from last years sale) and will stick with that version for now. Not enough to interest me in upgrading at this point for what I do. I've also bought a few Kontakt libraries from here and there, so I have pretty much what I need, without springing for Ultimate. I still use a lot of hardware synths & keyboards, so I don't use Komplete as much as I could if I was strictly ITB.
 
All in all, Komplete is almost a no brainer when it's on sale, considering the amount of content you get. It's a great bundle. If you're eye-balling Ultimate, then you really have to decide whether you'll use that extra content.

For updaters, it's not quite a no brainer.  A lot of the time, they release the next version of the software in the fall after the summer sale.  If you buy K10 on sale now, and K11 has some feature you need to have right now, you will have wasted your money on the K10 upgrade.  On the other hand, if K11 is postponed or doesn't look that exciting, maybe you should have upgraded to K10 over the summer.

The way I see it is if you have K9 or k9U like I do, there is probably no way you could have dabbled with even half the feature set extensively. There are tons of samples I haven't loaded and certainly a whole load of synths I haven't used to full potential. Heck there are synths in Reaktor I haven't even loaded yet.

Upgrading to version 10 would be a distraction away from my existing investment for me. I don't have time for Komplete 10.

Bonzos Ghost
I've got Komplete 9, (from last years sale) and will stick with that version for now. Not enough to interest me in upgrading at this point for what I do. I've also bought a few Kontakt libraries from here and there, so I have pretty much what I need, without springing for Ultimate. I still use a lot of hardware synths & keyboards, so I don't use Komplete as much as I could if I was strictly ITB.
 
All in all, Komplete is almost a no brainer when it's on sale, considering the amount of content you get. It's a great bundle. If you're eye-balling Ultimate, then you really have to decide whether you'll use that extra content.

I'm in a similar boat myself.  I took the Kontakt cross-grade > Komplete upgrade route last year during the sale, which was great, and having been loving every minute of it since.  Aside from SONAR itself it's been my single best and most used software investment.
 
However....  K10 just isn't quite forcing me to buy.  K10U?  Yeah, now that I could do.   If I only had the cash.     At one point I mis-read the $177 JRR sale as going from K9 to K10U, but was sadly let-down when I realized that it would still be $300+.    Ah well, there's always version 11...
 

I agree the African library is nice (and I imagine the Cuban one is also). But I can't see myself using them again and again, the way you'd do with say a bass guitar library or vintage organ library. Unless of course African music is your meat and potatoes. 

Magic Russ
For updaters, it's not quite a no brainer.  A lot of the time, they release the next version of the software in the fall after the summer sale.  If you buy K10 on sale now, and K11 has some feature you need to have right now, you will have wasted your money on the K10 upgrade.  On the other hand, if K11 is postponed or doesn't look that exciting, maybe you should have upgraded to K10 over the summer.

The way I look at it is, I'll never pay full price for a Komplete upgrade. I don't consider the full price upgrades to be good value for money. So I'm happy with waiting for the summer sale and being a little jealous in the fall when people start picking up the next version. The same thing happens when I buy a new phone - the new version's out in 6 months and I have to wait another 18 months for my upgrade. Having the very latest thing all the time just isn't possible unless you have money to burn. 

I just read on Facebook that when you upgrade from 9 to 10 some pianos disappear as they are superseded?

Is this really true? Um what about my fragile mix?