I used to be a notepad++ user.
Sublime is way faster to use and better all around and saves me tons of time(money) over using notepad++.
As far as the nag screen, I endured it for a while but I make money using sublime and enjoy using it want it to stay around so I purchased a license.
If the cost seems high, add the cost in to your next fixed cost project, typically clients aren't going to decline a proposal +/- $100. (don't list as a line item btw, just increase your quote by $100 to cover it).
You could also think about raising your rates. So you have more revenue for equipment/software.
Sublime has great time savers you might not have discovered yet.
This article is a little dated but covers some of the best things about sublime.
https://scotch.io/bar-talk/best-of-sublime-text-3-features-p...
This is a great series that shows off what Sublime can do:
https://laracasts.com/series/sublime-text-mastery
Speaking of raising rates. A great way to get better higher paying projects is to learn Rails or Laravel.