The UDRS is an ongoing topic of discussion, even during commentary of ODI series where it does not apply. As far as the Australian summer goes, the system could be considered to have served its purpose, at least in the Sydney Test, in making sure that post-match discussion didn't revolve around what would have happened if Australia were not gifted a wicket on the last day. However, it has also, here and elsewhere, provided talking points that could be seen as failures and negative side effects.
There is plenty to be said about the design of the system, its misuse and alleged abuse, but that's not my intent right now. The question of how the game itself may be changed by the current umpiring technology and/or the review system might be a less important topic of discussion, but I find it just as interesting.
In general, the system is intended to overturn out/not out decisions where the technology in use provides evidence that the original decision was incorrect. Even apart from which standard of evidence is used and the much-discussed misuse/abuse of the system, this means different things in different contexts. While a front-foot no ball should always result in an reversal, the gadgets are not set up to capture everything. It is more likely that compelling evidence of an edge will show up than similarly compelling evidence of a non-edge, while the use of cameras to judge the cleanness of catches can be a black art. It would be interesting to check thte figures to see whether UDRS has produced more reversals of out or not out decisions.
Let's turn to specifics. So far, the most extreme departure from human umpiring is the use of Hawkeye, which aims to provide the actual path of the ball and tell us where it would have travelled if the batsman had not been there, enough to completely answer the question of whether a legal delivery deserves an LBW verdict.
Kartikeya has already raised the issue of whether this spells the end of techniques intended to reap the traditional benefit of the umpire's doubt. Personally, I am amazed that this sort of technology is used in any context, cricketing or otherwise, without the presence of a serious treatment of its margins of error. Once present, there is a decision to be made as to whether this margin of error should be incorporated in the application of the technology. I believe it is consistent with the traditions of the LBW law and the motivations of umpiring technology, that a sensible margin of error be include. Without too much certainty, I expect that this would mean the age-old technique of coming down the pitch would still provide greater immunity from LBW, although not as much as we have previously seen.
The heat-sensitive cameras provide images that in theory should be fairly easy to interpret - they show a pattern of waves received at frequencies which our eyes do not detect, showing a difference between, say, a bat in normal conditions, and a part of the bat that has just hit a cricket ball. This can establish that there was an edge, although care still needs to be taken if the question is whether the edge came before some other impact in an LBW decision.
Apart from that, the evidence is not always there. The more angles, the better the chance of finding something, and it has been suggested that with only two (or one?) camera in play, players could game the system by turning bats one way or the other. More controllably, some stickers on the back of bats do reflect electro-magnetic waves in a way that appears similar to impact-induced heat on the HotSpot screen. Persistence with this technology should possibly lead to more conditions being placed on bats.
Finally, something that I haven't heard even mentioned by anyone else. It has long been wise for fielders to remain on the ball at least until an appeal has been given a positive answer. On at least one occasion now, a batsman has been given out LBW, the fielders celebrated, only for a reversal and an outcome of four leg-byes. At the time, it didn't mean much, but you never know when four runs could matter in a Test match, let alone the shorter forms if they also adopt a review system. With (dismissal) reviews in place, it is sensible for both teams to keep playing until the ball is dead for some reason other than a wicket. Having said that, I don't want to imagine the controversy that may arise from a situation where one team continues and the other doesn't, with a reversal of a wicket resulting in a run-out decision.