At one hand, it is written in a way that truly understand Ruby, but on the other hand, it is written very badly. It is written so badly, that it has a lot of SQLi bugs inside, it uses too many resources to perform tasks, and the list just goes on and on …
If that was not enough, then it is very opinionated on how things would be created, even on places that you need different level of thinking, it does not provide it on it's own, and you find yourself write stored procedures that implement them, or functions for triggers instead.
I mostly use Ruby "clean", that is not writing any web based application, and on one of the non web program that I wrote, I needed to go over million records per day (not literally a day, but day in BI), and I find that after 200 requests for records, it opens too many connections to the database, even though it has a limit for "only" 120 connections for it's connection pool, but when I decrease it for 50 connections, it claims that it does not have enough connections to use.
Even an hour of inactivity, it does not release it's connections back, even though it has a "timeout" of 30 seconds to release it.
It ignores my timeout settings, it just take more resources, but does not release them back, regardless of what I tell it to do. So it renders as resource hog, and you require to release the resources "by hand" rather then do it's job right.
I found, many complaints about it on the web, and even few bug fixes, that didn't really fixed anything as I can see in real life situation, even when going to the last stable release of it.
* This is a translation that was requested by few people for the original Hebrew post.