When it comes to swimming, form is everything! I am not exactly sure what TI is, but if it teaches you better technique and efficiency, go for it, especially if you are a beginning swimmer. Get rid of those bad techinques and practice drills, drills, drills. Bad habits will drain energy, as well as cause physical harm. It can destroy Your rotator cuff , and has been known to cause "hunched" shoulders because of poor elbow lift.

IMO the ultimate benefit of the TI method is to teach you how to be more economical in the water and commit that technique to muscle memory. Once it is engrained in muscle memory, it is difficult to just move on to something else unless you are working on fine tuning that technique.

What I like about TI is that the key concept that I took away was that power is generated in the hips; much like a golf or baseball swing. once the hips "snap" the rest of the body follows suite. Thats why when you see guys like Tiger Woods or Ken Griffy Jr. swing there respective weapons, it looks almost effortless. If you watch their swing in slow motion, the thing you notice is that the hips rotate first creating a large amount of torque as the upper body starts to catch up to the hip movement. The same concept holds true in the water.

Also your core area (abdomin, hips, buttocks) is a much stronger muscle group than your shoulder area. In fact the shoulder muscles are some of the weakest muscles in the body which is where alot beginning swimmers get their power. If you look at serious weight lifting routines that body builders follow, the two muscles that they recommend that you workout every day (because they can handle the load) are your calves and your abs. I say all of this because if you are swimming properly, you should almost feel more refreshed coming out of the water heading towards your bike than you did when you started.