[Zope] Connection pooling in Mysql

It's beginning to look like I need to do connection pooling for MySQL. A quick google turned up mxODBC from www.egenix.com which looks on-point but has a fairly hefty license fee for our systems organization ($100/zope instance). Anyone have any experience with the product? What other products are available? Also, wht's the threading behavior of the current MySQL database adaptors? I assume that database transactions are handled as critical sections and so threads block concurrent transactions. Is that correct? (Andy ... )