It's going to depend on the software. Some have a switch to use the watch instead of the phone. Some won't use the watch at all since that option wasn't available until S2. Many updates I've seen have stated they now use the watch instead of the phone.
Is it worth the extra $130? I think so. Outside of what's already been stated:
- The screen brightness may now affect you now but it could on an especially bright day and you may find yourself wishing you upgraded.
- The water resistance upgrade may such that you find yourself in a pool or other especially wet situation. You may find yourself nervous enough wishing you had the S2. The S1 will probably be okay, but you'll still worry until you know.
- If you ever get concerned about being in a movie theater getting an alert or want to check the time, the S2 allows you to turn the crown to slowly increase brightness until you can read the display. S1 doesn't have that feature for some reason.
- The S2 may "last" you a little longer where you may not feel the need to upgrade as soon as you might with the S1.
But no matter what we say, you asked the question. For that, you are already having doubts. If that continues and 3-6 months later you find yourself regretting staying with the S1 and go buy the S2, will it cost you more than $130? How will your budget be affected? Is $130 a lot of money to you? Stay with the S1 if it is.