Yes, most places will upgrade you for free and I have had that done for me through other companies. This is the first experience I've had with a company that didn't. Cheap company or not, it doesn't excuse them to operate this way on a regular basis, hence the warning to others. And yes, I should've checked reviews, but never had a problem with rental companies in the past so I wasn't expecting them to have a nearly empty lot.
As far as leaving a review here, I only see where you can leave reviews for hotels or restaurants, etc, not rental car companies. I did a search on this entire website and this thread came up. Seeing as others were giving their stories, I didn't see how mine was out of place.
Yes, I am leaving feedback in other areas. I use, and like, this site so I contribute here as well.