When I get a chance, I'll also see about setting up some benchmark tests for X-Cart so I can test the performance differences on my server (if any). Hopefully it actually results in a performance increase. I'll post the results back here.
Jayk, lemme know what you find out
Fastest way to find out, is to just go into X-Cart Admin, click on Summary, scroll down to where it's giving info about your server, click on More Info (or Details, can't remember) next to PHP, that'll show you your server's PHP Info page. Search for MySQLi, that'll tell you if it's enabled