It is very cool that enter now opens URLs in textmate.
Actually, this feature has existed for a year or so ;) just felt like mentioning in the release notes, as it¹s not directly visible.
So much goodness... So hard to find...
It would be a nice addition if, as in Safari and mail.app cmd-enter opened the URL without bringing the browser to the front-most.
The problem is that there is no API for that.
AppleScript does this for you without activating the application
tell application "WebKit" --activate --commented out to show the difference open "www.psy.ed.ac.uk" end tell
So that's one solution - I bet it is what mail.app uses. We could tell by snooping on apple events