When in the browser, if you tap the 123 you get a space bar. You don't get a space bar when you are inputting into the URL bar - there are no spaces in URLs. So some shortcuts I am training myself to do: use the search key when i really want to search; use the url bar when i know where i want to go; bring up a google home page when i want to search within the browser, or just hit the search button 2 times to get the quick search box, then hit the 123 key followed by abc to force a space bar.
None of this is elegant, but I really like the Samsung keyboard.