Please note that this post is mostly focused on the Services Industry rather than the products industry.
When someone approaches me and says "We should upgrade from X 2.0 to X 4.0, the word "WHY" instantly comes out of my mouth. Studying Computer Science in my early twenties I had the privilidge to have amazing teachers and to learn using the latest technologies available at that time. After graduating, I thought "now I'll be able to use all this new tech and it's going to be so awesome!". And then the chip dropped: most customers in the banking, insurance, telco & media, etc, don't use recent technologies. They have legacy systems that are working and doing their job brilliantly for years. They don't give a damn about what's new in the Microsoft tech stack: they want technology to help improve their business, which most of the times is not technology. And that's good: Technology is just a means to an end.
Coupled to this mindset, working "one step behind" the wave of new releases has huge advantages: the big "problems" are solved, the framework or whatever you're using is now stable and most of the "strange" issues and behaviors you encounter have already been discussed. Google becomes a really fast helper. You're able to really focus on solving a customer's problem instead of trying to figure out why "Microsoft, Apple, whatever, did it this way and how can we do some workaround".
Now, on the flip side, working with recent technologies is much more fun and will allow you to be on the edge of technology, always quickly renewing your knowledge. And this doesn't mean that the above quote is no longer valid. It still is: Technology is just a means to an end. It just adds the uncertainty of working with products that might not be as good as you expect them to be. And when doing project management, this has to be taken in consideration.
And that's the bad side. When working "on the wave", you're constantly facing problems that cut your productivity. Yes, Microsoft, Oracle, IBM, Apple, whatever, are all companies that are operated by humans that make mistakes and sometimes make design and implementation decisions that are questionable. And trying to decipher some of these decisions is sometimes exhausting.
So, is working on the latest technology good? YES YES!
Challenging? God, YES! I LOVE IT!
Always the best for your customer? It depends.