former hyundai owner here.
the new sonata (06+) is supposed to be a great car, and so far the short-term reliability reports are coming back positive. earlier hyundais were not as good. i had a 2002 elantra, and while i loved the design through and through (really fantastic car, if not for the reliability issues i had-- comfortable, roomy, thoughtful touches, felt like a step above what it was), it had too many problems and i was scared to keep it beyond the warranty period. i made sure i got rid of it before the warranty ran out.
as for hyundai warranties, they sound great on paper. the catch is that the dealers *hate* dealing with warranty repairs, because hyundai corporate is very strict about how warranty repairs are dealt with. for example, they don't reimburse the dealers the same amount the dealers would charge a customer out-of-warranty, so the dealers try to avoid warranty work in favor of being able to push the costs on to the customer. and, whenever a dealer performs a repair under warranty, a regional warranty rep investigates the paperwork and if they deem that the repair shouldn't have been done under warranty, they won't pay the dealer for that job and the dealer is out that money. i had to fight to get some things fixed that the dealer tried to push as "normal wear and tear", or the dealer would try to tell me that some problems were just "normal for that car". yeah right. ALSO, hyundai is very strict about maintenance. if you lapse on having the scheduled maintenance done on your car, hyundai will deny you warranty repairs if they can make any connection to the repair and the lapsed maintenance. for example, if the engine blows up and you missed an oil change, you're SOL... they'll say it was your fault the engine failed. i was a moderator on a hyundai forum, and i heard stories like this all the time.
so, upshot is they are pretty good cars now, supposedly, but be sure to budget money up front to have all future scheduled maintenance done *by the book*.
also, the 10/100 powertrain warranty does NOT transfer beyond the first owner, so if you buy a used sonata, you will not get this. you will still get the 5/60 B2B warranty however.
lastly, you will save money up front by buying a hyundai, but down the road you will lose value faster than a honda or a toyota. so in a few years if you go to trade the car in, you will not get nearly what you would for an accord or camry. i also learned this the hard way with my elantra. i got a fantastic deal on it... i thought i swindled the dealer it was such a great deal. then when i traded the car after four years, it was worth much less than other cars in its class. i could have driven a more expensive car (honda, toyota, mazda) for the same amount of time, and in the end, spent less overall per year of ownership than i did for the elantra.
:twocents:
EDIT: i don't want to come across as scaring you from hyundai... most of my problems were minor ones, not really major like the engine not starting. small things like electrical accessories not working, strange noises, clunks, etc.