I would only decrease rest time to a minimum of 30 seconds between sets. I really don't find that to be a great way to increase weight training intensity. If you're looking to increase the intesity of your workout try a variety of things: Pyramid sets, supersets, drop sets, more weight less reps, less weight more reps, more sets, different exercise routine, circuit train.
If you dont rest long enough between sets you're not allowing your body enough recovery time.
