Defenders of Ardania
This tower-defense game sets itself apart from the rest in one major way: the battle is multi-directional. What does that mean? Both you and your opponent have the ability to create towers and send units, leading to a back-and-forth style of control over the field as your units hammer away at the opponents base. This also allows the game to have competitive multiplayer, a rarity in the tower defense genre.The controls and UI are pretty clunky. The tutorial isn't very clear on what you need to do, telling you to press buttons by their action name instead of their binding. I restarted the tutorial once after getting stuck, and only make my way through it the second time after some keyboard mashing. Trial and error and a lot of looking up keys in the options menu finally led to a half-decent understanding, but still it's hardly intuitive. The UI isn't much help either, and feels off. For one, it's entirely non-interactive. In fact, your mouse cursor will actually go behind a lot of HUD elements, which feels quite odd.

Paradox games tend to be very non-user friendly and buggy, and this one is no exception. If the gameplay is rewarding enough, it's often worth it, but in this case I'd say it isn't. There is too much unit management, and not enough tower building (each level gives you a cap of towers that's usually in the 5-10 range). Add to that the UI and control issues and you get a pretty unappealing package. I personally have no interest in multiplayer tower defense, but if I were looking for a single-player experience I would stick to Defense Grid over this any day.
Cities XL 2012

For those who haven't played a game in this series I'll say that it feels a lot like Simcity but with less focus on resources and traffic and more of a focus on population. You have to balance providing housing, jobs and services for 4 different tiers of population, each with greater needs and value than the last. This is accomplished easily enough through the building of roads, zoning and buildings. The UI works well and the controls are simple but effective, making building a city relatively simple and quick. Money, while certainly a factor in your growth, is usually easy to come by, so long as you don't go crazy with the services.

If you haven't played a Cities game before, but you enjoyed the Simcity series, then Cities XL 2012 is definitely worth picking up. Compared to the previous 2 iterations, it's hard to say that anything has changed enough to warrant buying the full-priced game, and yet I consistently do, so that must be a sign. I enjoyed my time today and might come back for more in the future. I'm also looking forward to seeing how it compares to Simcity 4, but that is actually the very last game on my list, so it might be a while.
Notes
Two games from companies known for releasing buggy games, but one has had 6 versions to get it right.Album: Steam Challenge - Day 021