Personally, I had problems with the bupropion XL version. It seemed like the time release mechanism was not as effective, and tends to dump out larger amounts into someone's system at intermittent times, causing bursts of anxiety, as opposed to a steady stream of medication over a 24hr. period. With bupropion SR, I have experienced a steady release of the medication, which alleviates having to experience those sudden bursts of anxiety throughout the day. Is it just me, or has anyone had a similar experience with these medications?