I really see Coda/Espresso and Textmate filling two different roles rather than competing head-to-head.
For Rails development and other scripting, I use Textmate. I appreciate the extensive syntax highlighting, extendability through bundles, and the wide selection of themes. The lack of FTP built into Textmate isn't really an issue as I use Capistrano for deployment via command line.
For editing my marketing websites, basic PHP scripting, or anytime I need to edit and FTP files, I use Coda. It's a great all-around solution and almost worth buying a Mac just for it (and Textmate).
I tried Espresso after having used Coda for a while and just couldn't make the switch despite being a big fan of their CSSEdit. I primarily blame that on me getting so used to working with Coda.