In my experience, if it stops, but cars immediately start moving, it'll go automagically; but if it stops for more than 2-3 seconds, you have to push the gas/resume button.
So, I use it very frequently (daily commute, 60 minutes each way.), and I do share some of the sentiments above. It does leave a pretty significant gap, which other drivers take advantage of. If a car in front changes lanes, it does take a minute to register, which again, other drivers take...
Mine starts up about 5% of the time at this point, even from a very close range. When it works, I can't tell that I'm doing anything differently than when it doesn't work. Super frustrating.
I take it by your looking to upgrade the sound system that the 180w system in the EX - EX-L is, shall we say, crapola? I'm currently debating whether the audio system in the Touring is worth the upgrade from the EX-L.