I have installed W10 on two desktop machines that were running W8.1 and an underpowered elderly netbook running W7.
No problems with any of my machines nor my network which includes an old wireless multifunction printer, a NAS hard drive and two smart tvs.
Boot up time much quicker on all machines.
Seems to use less resources as nothing overheats or struggles, everything is faster and smoother.
W10 has built in 'cast to device' so I can quickly display the screen on to my smart tv.
Simple and straightforward to use once you remember that right clicking on the Windows icon opens up many day to day functions.
The search function bottom left is brilliant for finding anything on your pc.
I have not had any problems with program compatibility but I believe some have.
Downside:
No Windows Media Center but I have found excellent free, reliable alternatives.
Do you have any particular programs you are worried about?