I will just tell you right now that I'm pretty "anti-T78", so I don't want to be your reference point for buying it or not buying it. I was essentially fooled into buying it since I believed the following things at the time of purchase:
1. Lag is overrated
2. The divided housing makes all the difference
I can tell you with a straight face now that I don't believe either of the above items. However, let me make it EXTREMELY clear that my own powerband and power goals might be completely different from your own, so you should ask yourself what you want.
My decision criteria (when I purchased the T78) was to make 500 rwhp relatively easily on the stock fuel system, and it handily exceeded that goal when I made 514 rwhp at 17.4 PSI. However, my original goal had no powerband implications, and I didn't care for the lag associated with the T78 (67mm wheel, 1.00 A/R). I have since spent considerable time and money to achieve a quicker spooling setup since then, and wouldn't have purchased the T78 again (but would have started with a flexible turbo kit, such as the BoostLogic setup).
Again, ask yourself what YOU want. If the following sounds good, then the T78 may be right for you.
1. High quality and relatively affordable kit
2. Ability to make 650+ rwhp with supporting mods (clutch, fuel, tuning)
3. Good "all around" single turbo setup...medium sized
Hope that helps! Again, you should listen to other T78 owners who continue to stick with them, as I barely scratched the surface of what it could do. It was "too much turbo" for my liking and my overall goals (which have been heavily refined since owning a T78). The things I don't like about the T78 are not shortcomings of that kit whatsoever.
I hope that is a fair account.
Steve T.