There is nothing wrong with using a clone browser if it keeps the vulnerabilities patched and offers features not included in the original that can not be duplicated by extensions. Pale Moon includes all of the features removed from Firefox 29 plus has a 64-bit version and is optimized for better performance. It is more customizable, supports full themes with Personas and supports all of the extensions broken by Firefox 29. Most browser clones really don't offer anything special that can't be duplicated by extensions.
View the
comparison table of Pale Moon compared to Firefox.
Enjoy!!