I don't have any particular problems.
I am not particularly smart and yet I managed to improve the DD-WRT Wiki article on Chillispot:
http://www.dd-wrt.com/wiki/index.php/ChillispotIt took a DAMN long time though

So I hope you like it.
I think it answers all your questions. I read the above comments. Did you read the Wiki?
Coova is fine I suppose, if you want to use the OpenWRT interface which is not as mature or easy as DD-WRT
And if you do not need the other DD-WRT features. I don't use Coova.
Usually it's enough on a 16meg RAM router to not have the Web interface startup automatically.
This leaves enough RAM for chillispot to run effectively.
See the chillispot article.
You should also be using build 13064. Rock solid.