When I first got my sub, I thought the safety cage looked a bit clunky and assembled it without it.
I minorly burnt myself 2-3 times that first night and promptly installed the heat cage.
I haven't burnt myself since
To further add to what
@Sublimator427 said, the heat cage doesn't protect you from the atomizer when they are separated.
However, I've found when the sub is in use, the ONLY time my heater and atomizer aren't connected, is when my heater is sitting on the Z stand and I'm emptying or reloading the sub.
Given how much attention is required of the sub at those times, I find burning myself is of no concern (I also have an appropriate scoop to aid in loading the hot atomizer - everyone should have some kind of "sub spoon" IMO
)
That little metal bar that attaches to the heater is still exposed, and a potential burn risk, but I personally have never grazed it or anything, so I don't know how much of an issue it'd be for other people.
I've found that the bottomhf of the heat cage always stays pretty cool - cool enough that it can be picked up by hand once the sub is fully heat soaked.
I'd say the top half of the heat cage could potentially burn you with even moderately prolonged contact, but a quick graze wouldn't burn.
It's "touch it and it stings" hot if that makes sense
It makes me feel a lot more comfortable with the sub, but I can also see how it would be incredibly easy to just never use it.
I think it makes the sub look a bit more clunky
, but the usage benefits outweigh the aesthetic defects for me