I would say yes, and then I would say that at the same time you should move away from using IE as quickly as possible. Microsoft has, to be fair, made some impressive strides security wise with IE since it left IE6 to rot for several years, but it's still a very long road it has to travel.
So for those few times when using IE is completely unavoidable, you should always be using the latest version to ensure it has as up to date security as is possible for IE, but for the other 99.99999999999999999999999% of the time you should be using something else. Pick any one from this list and make it your new primary browser, relegating IE to those times when you absolutely cannot find the same content any other place, and the site absolutely will not work with anything other than IE: Firefox, Opera, Chrome, Safari. Pick one of those 4, doesn't matter so much which, leave IE alone.
You would also probably be wise to look into Foxit Reader to replace Adobe Acrobat Reader. Then if you're not using IE, there'd be little need for Malwarebytes, disk cleaning programs are scams so you can dump that any time, CCleaner has its uses but I find the majority of people think it's some kind of magic panacea program so if I'm saying anything that seems even remotely like news to you, you'd probably be better off getting rid of that too. And then after a little quick googling, iobit seems to be one of those registry cleaning/system optimizing scam programs, so I'd dump that too. Those programs cause way more problems than they ever resolve or prevent.
Sorry to dump all over you like that, especially when you asked what you thought would just be a simple question about IE9, but in the long run it'll be a good thing.
Microsoft keeps prompting me to upgrade to IE9 but I'm apprehensive that I may experience a pile of problems if I do so.
I am running Win7 Ultimate 64 bit with IE8. This was a clean install on a homebuilt pc. My a/v is Avast.
So - appreciate advice on what to do: Should I forget it or install it from Windows Updates? What kind of problems should I expect to have during the install?
Will I have problems with the other common applications I use such as Malwarebytes, CCleaner, IOBit, Adobe, Wise Disk Cleaner, etc.?
I'd appreciate any advice and comments I can get.