My early 2009 iMac was still working well, but it was limited in ability to run the newest software.  It had a 24 inch screen, so it was a large one.  I upgraded to this late 2015 iMac with a 21.5 inch screen.  The better resolution on the new Mac makes the smaller size be no problem.It came with El Capitan operating system, the same as on my previous iMac, and I was afraid that I would again be unable to upgrade.  However, after transferring all of my files to the new computer, I downloaded and installed Mojave.  Man, it works well!  Faster than my 2009 iMac and with new abilities.  I don't know why the refurbisher did not install the newer operating system (2 steps up);  it is free.One thing I had to adjust to:  I used Excel on my old Mac.  It was an early version of the spreadsheet, bought when I did not have to have a subscription to use it.  I was happy with it.  However, with the new iMac I am unable to use the Excel spreadsheet except for read-only.  The same is undoubtedly true for Word, although I haven't tried it.  (Somehow Microsoft knows when you change machines and try to transfer Excel to the new one.I use a spreadsheet for only 1-2 hours per week, and I refuse to pay Microsoft $60 a year to use it.  So I opened the 8-10 Excel spreadsheets into Numbers (Apple's answer to Excel).  Some things are different, especially graphs (which Numbers calls "charts"), but I have been able to to everything with Numbers that I did with Excel--and Numbers comes free with Mac.  I can even export a Numbers 'sheet as an Excel spreadsheet for my few Windows friends.I have used Apple's Pages rather than Word for some time, so that is no problem.The computer came with the small Apple keyboard and mouse.  I had a large keyboard with a number pad, and I will continue to use it.  I do like the Apple mouse, however, and am using it.Needless to say, I am extremely happy with my iMac, as I have been with all things Apple.