I am waiting to install OS Sierra, because I heard there were problems - slow, etc. Is it safe yet?

I have installed it on both of my Mac and not had problem one. Also the users I support have not had any problems either.

The only suggest I have is to first backup everything just in case. When undertaking a large project such as an upgrade of the operating system, it is always good to have a backup.

That depends on you, is your Mac ready for it, have you checked that your Apps will work, have you removed the ones that won't, are there any problems with it now etc etc.

I downloaded Sierra on both my macs and did not have any problems

dobob wrote:

Are there still problems with OS Sierra?

All new OS's have problems. It's the nature of providing software that runs on different systems with different third party software and hardware. It is safer to wait or simply review everything that is important to you.

The questions you need to ask are…

1. Does your Mac support 10.12?
2. Does your third party hardware support 10.12 (e.g. specific add ons like midi devices, printers, scanners, cameras, video cards etc)
3. What OS are you moving from (10.4.8 is really old, are really you still using that or do you mean 10.8.4 or something else?)
4. How good is your backup (ideally you have multiple ones so you can keep one backup 'frozen' and another for use with 10.12). One Time Machine backup disk is not enough.
5. Does my software run on 10.12?
6. Will you upgrade or erase & install?
7. How quickly do you need to revert if it has problems - that effects how you make backups.

As for #5 check roaringapps.com or ask here if you have specific application needs.

It's probably going to be smooth if you prepare & have a fairly clean Mac, if you have years of old apps & an ancient OS the upgrade may not go so well.

I heard there were problems - slow, etc.

Truth the the first casualty of macOS upgrades.

Please read Upgrading to macOS "Sierra" without fear.