If you live in an area that doesn't have a lot of blackouts (loss of power) then it really isn't necessary. Retail stores spewed a bunch of bullshit in the early 2000's that if you didn't have a UPS and there was a brownout/blackout that new computers were so powerful they would blow up and would give stories about people who just came in weeks before and bought a new computer and chose not to purchase a UPS and a power outage fried their $1000 dollar.
They are great if you do important work that can be lost to power outages, but simple regular saving can fix the problem, and a surge protector is more than plenty in protecting from lightning strikes and it takes a massive over voltage, much greater than grid fluctuations to damage computers and other devices.
If brownouts/blackouts and large voltage spikes are a concern to you, then they are great, minus the fact you have to replace the battery every three years or so even if it never goes to battery power. They don't last as long time wise as they are rated for. A 500W rated for 1 hour at 500W draw may give you 30 minutes at half power, if you are lucky, on a brand new battery. As the battery gets older, they get much worse and eventually stop working. Replacement batteries cost typically about half the price of a brand new UPS so most people just buy a brand new one when they go bad.
If its really important you would be better off getting the more expensive $1000+ UPS devices, if not, don't really worry about it. They do still work great as a surge protector, just don't expect the battery to last long.