Just wanted to chime in from first hand knowledge that the CRJ cargo compartments are pressurized. They are not however always temperature regulated so freezing may have been a factor. There are many other aircraft that don't have regulated temps in the cargo compartment even though they may be pressurized. That is why many airlines gave up carrying pets in the cargo compartment, also because the fire extinguishing system removes all of the oxygen and will kill anything in the compartment.
Also, and this may be news to some divers, baggage handlers are nicknamed "apes" for a reason (no offense to my ramp friends). They don't always gently place your bag in the cargo compartment like it contains delicate instruments. Many times they are literally tossed on or off the plane. They fall from the bag belt during the loading or offloading process and fall 7'-20' (depending on the aircraft model) from the cargo bin to the concrete ground. Even in the cargo bins other heavy bags are loaded on top of your softside dive gear bag or other bags fall on them. I once watched a duffel bag with a dive flag on the side fall from the cargo bin of a Boeing 767 to the ground at one of the islands.
I never bag check a dive computer because of the chance of freezing damage, rough handling, or abuse. I'm not saying that this is the case with all baggage all of the time on all airlines but it does happen. I always want to know what its been through. I value my safety a bit too much to do otherwise. I advise all divers who travel with me on our trips to do the same. My Cobalt and my Wisdom before that were both quick release air-integrated so that I could remove them from the reg and take them with me in my carry on bag.
Yes, I prefer the Atomic Cobalt over any other dive computer that I've used.
Larry