Bought my 06 tC in may 2006 with 53 miles on it, now up to 210,000+ miles.
No major issues what so ever. I still have the original car battery, which is impressive. I did have to add some distilled water into it after 6 years, no big feat there.
I have a short RAM intake, Borla axle back exhaust, which after adding bumped my MPG to about 31-33 hwy.
Most of my driving is hwy, my daily commute is 60 mi each way. and I drive frequently from San Diego to Sacramento, roughly 550 mi each way. The tC is comfortable enough to drive the whole way with no problems. I'm 5'10".
Very easy to maintain. Easy access to the oil filter, I always check the placement of that on cars before buying.
I bought this car for all the features, everything comes stock on a Scion, power windows, mirrors everything really, pioneer head unit, nice speakers, tilt, cruise, moon roof and sun roof, good MPG, AC, reclining back seats, leather wrapped steering wheel, etc etc. why pay more for what should already be there?
Longevity is good. allthough so long as you maintain your car, it will last.
Interior is nice, I've driven some "nicer" cars like Infinities and BMW's of the same year and was surpirised by the quality of those brands interiors, that is after all what you see and feel while driving.
More HP is always good.
Streangthen the trunk handle area.