For me, the ability to be able to delete some of the bloatware that comes with the iOS system is a big plus. I don't know if it takes away anything that I want yet, but I will find out and decide for sure as soon as more people download iOS 10.
The Apple iOS10 update is the biggest and has some exciting features. It is worth it to update because the improvements will help to maintain a more efficient use of the IPhone. There will be a new Bedtime function to set the number of hours that you want to sleep. Other updates include 3D Touch, News and Music.
If you use a conventional IMAP account, and often utilize folders with a lot of messages, you may want to hold off on upgrading to iOS 10... For whatever reason, iOS 10 will only load a maximum of 150 messages per folder with conventional IMAP accounts. Google-IMAP doesn't seem to have the issue, but if the email account was set up as an "Other" IMAP, your message scrolling to the bottom of the message list wont load more messages from the server as it has in the past. This seemed to crop up with the 10.0.1 GM release.
A basic smartphone works just as well as the latest versions. The truth is, smartphones, no matter how many times their operating systems are upgraded, will never replace the laptop or the desktop. If you have a phone and it's not letting you do what you need, switch to a laptop because phone are meant for communication not for work.