Samsung Galaxy S owners in Germany to increase talk time to 8.5 hours

Samsung Germany sent out an email newsletter with its plan to provide a battery-enhancement pack, the Samsung power pack EBB-U10. It not only replaces the battery, but the entire back case. According to Eurodroid (via TalkAndroid), the battery pack provides 8.5 hours of additional talk time and 500 hours of standby. This might be worth it for those heavy users to get that extra time in, but would you sacrifice the slim design?