On a scale of GBA backlight to DMG backlight (easy to hard) it's pretty much smack in the middle, right next to gameboy pocket backlight (with worse results). Only instead of peeling and freaking out about about the reflector, you're dealing with LOCA which is both an added expense and an added annoyance. One that you may not even realize was botched till days or weeks later via spidering.
Also, if you're had ANY other backlit gameboy, the frontlit color is going to feel like a downgrade. If it's your first gameboy mod, yeah go for it, it's definitely a good beginner project just because nothing is necessarily hard just a little frustrating if you don't take a ton of precautions, and you'll definitely pick up a few new skills. If you're looking to turn that GBC into your main gameboy workhorse for games however, hard pass. The results would have been acceptable in 2000 but in the era of everything being backlit it feels unplayable compared to any of the other options.
(Edit) Here's a couple quick comparisons.
On brightness:
https://i.imgur.com/Kuwrd5Q.jpg That's with a 'standard' 1 cable install on the GBA (also known as 85% brightness, or no voltage regulator). Don't mind the 'scanlines' in the GBA pic, it's only picked up on camera.
Focusing on the GBC so you can see the washed out nature:
https://i.imgur.com/kIw91W9.jpg only thing to note is that there was a scratch on my front light which produces a bright spot. Otherwise you get a pretty clear idea of just how muted everything looks, and it looks worse the closer you get to the bottom where the LEDs are.
About the only benefit the GBC has is that you can use it in direct sunlight even with the front light, but it's still going through the textured glass so it still doesn't look as nice as a stock. Oh and you can play it at all at night... but again, every other option is just superior.
