I've had very good luck with my SC on my 1997. It was put on the vehicle because I tow quite a bit. It makes a night and day difference when towing anything relatively heavy (my load runs a little over 4,000 lbs). I've been very pleased.
My thoughts on a few issues that have been raised:
1) I've installed about 1/2 dozen FI kits on different vehicles and the parts list, fit/finish and quality of the TRD unit exceeds the others. The install is easy as far as FI units go and its "OEM like" in its behavior. It feels just like a bigger motor.
2) My understanding is the unit fits and works better on the 95 & later vehicles than it does on the earlier ones. This is mostly an ECU issue.
3) Several people mentioned detonation issues. Some of this is a function of the octane level of the fuel in your area. I get 93 octane, some folks (Arizona, Colorado & California come immediately to mind) have to live with crappy 91 gas. If you can get the 93 in your area I would not be too concerned with that issue (other than the cost of fuel).
4) To agree with others, the vehicles cooling system must be up the task. A clean well functioning OEM set-up should be fine, you should not have to upgrade. But a neglected system might not be up to the task.
5) If I were purchasing a truck with an SC already on it, I would be particularly concerned with the maintenace of the truck.....even more so than normal. If everything has been well maintained, I'd be willing to pay $1,000-$1,500 more than I would without the blower. If you can't get comfortable with the maintenance of truck, I'd walk away. Certainly it would not be worth anymore, if not less than one without the SC.
My 1/2 cent,
Mike