It's funny, my lax tea did nothing for me last night and I used a fresh tea bag and full steep! I woke up with cramping and 'went' but only VERY lightly. I do the swf (actually much easier so far than when I tried the Master-Cleanse the first time) with visuals in mind. I imagine colon sludge being washed out with the salt water. I'm not sure how a laxative can get mucous etc. out as well as the swf.
It's a love/hate on the swf's with me - probably you too I guess? =) I would recommend doing it for the wonderful flush especially since you haven't done it thus far. We'll wait to see what the more experienced say!