Something similar happens to me every now and then. I will charge the phone to 100%, but as soon as i unplug it, it drops to 99%. My advice is to drain the battery to at least 20%. Then charge it back up without unplugging it. Battery issues are very common and Apple is hopefully going to fix it with OS 3.1 (or so i have read). And even so, is it being 2% short of a fully charged battery really that big a deal?