Feasibility of using XML, PHP for a database-driven web application

Hello, I've been doing some research to assess the feasibility of using PHP and XML for a web-based database-driven application. From what I've read, it seems that presently the costs of using XML outweigh the benefits. Here are the costs I see: 1. XML standards are still maturing 2. XSLT is complex and difficult to understand 3. Their is minimal support for XML in relational databases, and none for MySQL 4. PHP's XML tools are still in their infancy 5. The processing time to go from SQL to XML to HTML via XSLT is often high. The benefits? 1. Greater abstraction between data, logic and presentation which can be easier to design, develop and maintain. Your thoughts? Thanks, Gerry Kirk