I've been using RMS Flitesoft (rmstek.com) since the time when it shipped on floppy disks and it works pretty well in addition to being one of the lower cost (on an annual basis) of the non-free applications. The initial cost is $200 (FS-Pro) and the annual renewal is $120. For that you get all updates to the planner application and it's database plus (relatively automatic) downloads of sectionals, and low/high enroute charts. The only dislike I have is that the program is a port from something other than the Windows environment and therefore doesn't follow many MicroSoft conventions (no file open dialogs etc). It has gotten more "Windows like" over the years
in addition to getting more powerful so maybe some day they will completely adopt this environment (assuming that's a good thing).
Another interesting feature is the ability to load the entire application and database onto a USB flashdrive and run on anybody's computer that has a USB port without actually installing the program but I've never used this as I always carry my laptop on trips.
I also subscribed to another flight planner called FliteStar for many years and I still think it's a slighty superior application but it costs a bit more annually, comes with less, and when Jeppesen took over the program a while back they got real snotty about multiple installations. When started using the program I had it installed on three computers, one at home, one at work and one laptop for travelling and this was in compliance with their license policy which only required that there be one license (fee) per user. Jeppesen changed that policy to limit a single license to no more than two computers and insisted I pay for a second license if I wanted to install the program on three computers for my personal use. I went along with that, foregoing the installation on my desktop at home but then I ran into a related problem a year or two later.
The final straw was when they accused me of pirating their software after a bug in their installer and subsequent advice from their support desk required me to re-install the program on a new computer several times before the problem was fixed. Then when I needed to transfer the program to a newly acquired computer at work, they said I'd used up all the installations I was allowed and it was obvious I was trying to cheat their piracy protection. At that point I terminated my subscription. To be fair, there were several years during the transition to Jeppesen control of the application when their support services were "somewhat suboptimal" but I suspect that they have improved since then.
That said, one feature that Jeppesen's FliteStar supported that I miss in FliteSoft is the the ability to save multiple routes between two airports in one file. This capability was very well implemented and I found it quite useful for trips I commonly flew since it allowed me to easily select a previously established route to accommodate different winds and weather that needed avoiding.