I've never really been a fan of Toyota products in general, but I always admired their quality and reliability. In my opinion their performance and handling, or design usually left something to be desired... In the case of the Prius it's just handling that's an issue, and that's pretty decent, just could be a little tighter. One of the things the engineers had in mind when building the Prius was to make it reliable, avoiding the usual stress associated with things like accelerating hard and even hard braking, on top of using a less wear prone gear system where most of the torque is applied to the wheels
outside the planetary gears (on the ring gear), the ICE is protected from sudden changes in load making it wear much less. It seems all 'new' and mysterious, but really it's an older, simpler design with modern computerized control mechanisms and all the rest of the improvements in technology to squeeze the most out of the system while minimizing the amount of pollution.
This is where the car's weakness is as well, because typically older vehicles will have electronic circuit failures as the electrical system ages and things corrode and decay. Unfortunately that's not really any different than the Honda, it's got plenty of electronics running the show other than the hybrid system, so as
all modern vehicles age they will be prone to electronic system failures at some point. It's interesting that Toyota built a semiconductor manufacturing plant for the systems in HSD so they can custom design the components for better durability in automotive applications and so far the only serious thing that I've ever heard of going wrong in a Prius I is the Panasonic battery eventually dies (100k+miles) if you don't have it serviced to clean, then re-seal the positive terminals that weren't sealed adequately in that type of battery. If the battery really is the only serious failure that occurs at some future point, and of course that future point is 8+ years because of the warranty then it's still worth popping a new, or rebuilt battery in and finishing off the ICE, or whatever comes next...
I honestly don't see much difference between the Honda and Toyota hybrids in the long run, both are going to need mechanical or electrical repairs as they age. The Toyota may cost hardly anything in repairs for a very long time, then when the battery goes it will cost you a bit more than usual as far as repairs usually go, but nothing too extreme. The Honda will have more mechanical repairs, each costing less than the battery in the Toyota, but adding up to as much, or more than the battery, plus if you wanted to retain the full functionality of the car you'll be replacing the IMA pack at some point, possibly even before the average Prius needs it's pack replaced. It's really hard to say at this point what will happen. It will be very interesting to see the statistics as they roll in.
There are some very preliminary results
http://www.hybridexperience.ca/Reliability.htm showing Prius as having the lowest 'Non-Scheduled Maintenance' between the Insight and the 'ol favorite fleet vehicle, the Cavalier. 2001 Prius cost $0.19/100km, Insight cost $1.78/100km and the Crapalier cost $2.69/100km. The Insight and Prius cost more than the Cavalier for scheduled maintenance because they took them to dealerships rather than the in-house service the Chevrolet got, but if they weren't chiken about changing the oil, then it would probably be pretty even for scheduled service, perhaps a little higher with the other various fluids to change.