Limitations Question

I'm a college student learning Ruby on Rails. My instructor has given
me a good basis for designing web based solutions with RoR and we've
looked at Ajax and script.aculos.

I've seen posted on various sites about Ruby being great or Ruby being
the root of all evil.

As a relatively new programmer, I need to know what limiting factors I
should look for before starting to develop within the enviroment.
Alternately, where does it shine, and where is it very difficult to make
work? Are there speed or size issues? Does it not play nice with
established systems?

The reason I'm posting here is because I would like a professional and
unbiased opinion from people that have worked with it. This seems to be
very difficult to find on the web.

I did a basic search on these forums and didn't find much addressing
this. If some has already been answered please post a link to the
related topic.

Thank you.