What are the implications of downgrading from 2.5.1 to 2.4.1 on a Joomla 1.5 platform?

I inadvertently installed 2.5.1 on a site under development and have been issues with the styling. On further investigation I noticed that the k2 css file is not being included. I suspect this is a bug.

I would prefer therefore to downgrade to 2.4.1 but am conscious that this could impact upon the site which already has a number of K2 items (articles) added.

Please could you advise.

Thanks in advance.