I do not have a 2010/11 Hyundai Santa Fe, but I got a 2008 diesel fully loaded brought down for a transferable permit. I have done 60,000 km now and its safe to say that I have had no trouble with at all. There has not been a single failure in car. All I have done is to service on time through the agent.
It does around 9kmpl in cmb, and around 10kmpl outside. but this really depends on driving habits as I tend to push the car to its limits most days... off road capabilities are fine up till now and haven't been stuck any where, but the slight issue in that is the ground clearance as it stand its only 200mm compared to a prado which is around 220mm..
Performance vise, it can easily take on other Japanese SUVs such as the Toyota Prado or Montero. This Im saying is because I got them in my family and we always race to check which is the fastest..
As the question is about the gears, there is a bit of issue there which let the car down. if you are really hammering down the gear shift in automatic mode is not very smooth and it is out of thoughts as when to shift. so wiser ppl would go on to triptronic shifting which is better, however that too has a considerable large lag time shifting between gears. However neither of these take place if you are driving sticking to road laws though as in low speeds its smooth when using automatic transmission.
Before we brought this many people told us that Korean cars are unreliable, but as usual those toyota freaks are always wrong, my brand new Honda Civic is giving me trouble and not this. ppl also complaints about suspension, and I haven't experienced that either as its extremely comfortable and no noises..