Question: I bought my base model 15" MacBook Pro w/ Touch Bar the day it was released, and I just received it yesterday. I've been copying and downloading all the data and files that I needed and the battery didn't last me more than 5 hours, if even 4. I have no idea what is wrong with it, but it's really overheating and I almost never hear the fan running, which also alerts me.

Today I played Crossfire, a game with very basic graphics, on Windows 10 Bootcamp and it was ON FIRE! I had to close the game because of the laptop's temperature. Again, I did not hear the fan.

Things I've done:

* Reset the System Management Controller (SMC)
* Run hardware diagnostics by restarting and pressing the `D` key while booting. This was the first time I actually clearly heard the fan. The overall results were that it found no hardware problems.
* I called Apple, but they had no idea what they were telling me as they were following a written script, although a Senior Advisor was talking to me regarding the issue.

Now I have had it just for two days so far, and I have a two-week return period. Should I wait more and see how everything will work out, or should I return it?

Has anyone experienced the same issue? Is there anything else for me to try?

Answer: 
The problem you discribed is exactly the same that I have with my new MBP 15" Touchbar (2,9Ghz, Radeon 460). 
The reason why it's overheating is, that the fans do not automatically accelerate when there's a higher workload. They are continuously running at 2000 rpm. 

My solution: Use iStat Menus

There you can manually increase the rpm to medium (3500-4000rpm) and high (4500+).
You will see, if you manually adjust the fans, the MBP will work great and there won't be any overheating issues.

BUT that's not how a notebook should work. It must automatically adjust the fans.
I talked to several apple support guys (In Germany) and they all told me, that they havent experienced such a thing yet. I did the same things like you, resetting NVRAM, resetting SMC and I even reinstalled the OS. Nothing helped.

It may be a firmware issue that will be fixed in the future. However it seems like just a minority of MBP Touchbar customers are facing this issue.
Most likely I will exchange my notebook in January (since it's not available at the moment xD )
A brand new computer should not give you such problems. I would return it within the two-week time window and ask for a full refund.

Some people I work for need to buy new MacBook Pros, but it's hard to recommend them right now. For one person in particular, battery life is crucial. Everything I've heard so far about battery life, the new Apple MacBook Pros are lemons.

It's very disappointing, especially since it's been such a long time since these models were updated — people have been waiting for them. They're not selling these new machines any cheaper either, they ought to work at least as good as the previous generation!

Hopefully they'll come up with a revision that fixes the issues — meanwhile, if you can still get a full refund on your brand new MacBook, that's what I'd do.