I did this once very early in my career. It was a same company, different departments situation. Not sure how this relates to a 40 year old in today's times or compares to a relationship in 1988 but here are my pros and cons:
Pros
Access to pussy any time of day, in elevators, empty offices, in the parking lot at lunch, the roof of the building, etc (keep in mind when I did this it was long before security cameras covered every inch of a building and the whole hostile workplace really wasn't a thing yet).
A very "streamlined" life ..... it's REALLY easy to make Friday night/date plans and you have things buttoned up by 3 pm. So there's no conversations at 7 pm around "so what movie did we decide on"
Commuting together the next day if the prior evening ran long. This is an incredible opportunity for road head on both the drive into work AND back home.
Might sound crazy but, the ability to just keep an eye on things. If she's involved in any shenanigans or other sorts of general Fuckery, you know because you are there and see it with your own eyes.
Cons
Everyone you work with knows ALL your business
When things go south coworkers take sides. This makes getting shit done in a collaborative way very difficult. When my situation ended, a female co-worker refused to even speak to me.
When things go south one of you will probably have to find a new job if the masses are against one side or the other
When things go south, If you are into any weird or fetish shit, every single person, including SVPs, EVPs, district Presidents, etc you work with will know about. "Did you hear he likes anal more than regular sex." "She told me he never wanted to have sex and just wanted blowjobs." "Did you hear he tied her to the bed and didn't let her go until she cried?" "I heard he gets blackout drunk every Friday." "Did you hear he asked her to set up a threesome with them and Sally?"
For me, it was an amazing situation until it wasn't. And once it "wasn't" ..... boy did it suck! I vote no.