The complete TC kit now comes with the bubbles style too, they changed it recently. They didn't drop the price though! Note the disclaimer down the bottom of that link.
The cars these days are so much better balanced with lipos than they were with NiMH batteries, so you find that tweak due to L/R balance is minimal. When I rebuild my car, I always check it, but with my current electronics and using std battery offset (Salkin, you can adjust it on the 418 by adding/subtracting spacers to the lipo stopper) it's always perfect.
So to answer, "need" - hmm, nah. Not really. You can achieve 90%+ what the tweak station does with the $10 balance pins.