BurnTool is a SFX 7zip file, you can look inside it with 7zip, inside is the program. It IS SAFE to use and is not malicious, however, it can trigger a false positive with some AV.
It's not too hard, and there are instructions on the site, but trying to connect to WiFi without reading instructions may be confusing at first. Once you remember to select your wireless adapter from the dropdown menu, its super easy.
Hiren's Boot CD is very popular. Anyone who has ever worked in support or system administration probably has used it at least once.
Because of this, it's extremely easy to find guides and tutorials on how to use it, or if a tutorial does not explain everything, chances are that you can find someone to help you with it.
Its "popularity" is not a reason to add any PRO. It has gained its popularity because of high level making. Most of that popularity was at the time it included all commercial products such as Acronis, Paragon, Symantec, etc.. It's only after version 10.4 that those apps were dropped out.
There is also no reason to qualify it in CON only because it's outdated as it was discontinued years ago.
For users that still run Win XP or Win 7 it's still relevant in most cases. You just have to realize that it was built at a time when common systems was based on x86 architecture, not x64 one.
Being initially designed for Linux users, it can be hard to use for people that are used to the way Windows programs are designed, especially because Trinity Rescue Kit has a command line interface.