I'm way less knowledgeable than many in the forum re: software, but I'll just say that I upgraded from Komplete 7 to Komplete 10 last month and am thrilled that I did. With the sale prices at the time, I moved up to K10U but would have probably just bought K10 based on the spring deal anyway.
I'll echo one thing I hear repeatedly but didn't necessarily understand at the time: you probably won't use everything in the package...there's just so much on offer and across such a broad musical range from orchestral to EDM to cinematic and all in between. Many effects/VSTs with so many sounds. That said, the $$ value of all the components in one package is compelling to say the least, and it's REALLY helped me look the other way when other software goes on sale. Not that I don't covet said items (like everything Nomad or BFD3), but the little voice in me head says: "you haven't even loaded X, Y, or Z Komplete plugin yet - work with what you've got!!!" Then there's the part of me (my wallet) that say's "there's nothing in here." That also helps keep the GAS levels down. I even averted jumping for ST3 at the cost of a cheap controller - the small corner of logic in my brain convinced me I would never to get all of those instruments, and in doing so I would probably not fully realize the value of the NI treasures I get through Komplete. I just wish I had the time to buy both and use both.
Kontakt alone is a great reason to jump; the NI user forum has a lot of great Kontakt and Reaktor instruments that I'm starting to go to more frequently, too. I don't spend nearly enough time on music and will probably spend another year discovering new applications for even the regular K10 software (The Giant! Session Strings!) but am quite the amateur in all aspects.
All that aside, it's a good value right now and the NI sales are the best way to jump into future versions should you want to, be it cross grade or upgrade/update.