It really depends on how you use the tool. If you only need occasional help with tasks or specific work, the free version still works fine. The problem is you hit usage limits per hour, and when lots of people are online it gets slow or doesn't respond, which is frustrating when you need something urgently. With Plus you get priority access, faster connection, and you can use GPT-4, which is quite a bit better than the free model for complex tasks.
Now, $20 a month is pretty steep when you think about it annually. Before you pay, try alternatives like Google's Gemini (free, with access to powerful models), Claude (has a free version that's very capable), or even Microsoft Copilot. Some of these models work just as well or better than ChatGPT for certain things, and many don't have such strict usage restrictions on the free plan.
My recommendation: try a couple of alternatives for a week and see which one fits better with what you do. If you really need the speed and reliability of Plus because you use it heavily, then yeah it could be worth it. But if it's just every now and then, the monthly cost isn't worth it when there are solid free options out there.