This movie tends to get a lot of flak, but overall it is pretty entertaining. It's essentially Duncan's Highlander II, but with less aliens and slightly more believable immortals (I loved Highlander II, but the flying immortals at the beginning were a bit much). It takes place in a dystopian future where the world has descended into chaos as a result of a coming cosmic alignment. One thing audiences fail to take into account is that Highlander movies are historically low-budget, save for the first Highlander movie (its budget hovered around 15 million, about 30-35 million today). None of the movies was given a budget exceeding 20 million, and the TV series, as it was syndicated, wasn't much better off. So yes, the effects look low budget because they ARE low budget. You expect an Infinity War (or even a Matrix level) level project in 2007 at a mere 13 million? Not gonna happen. For what it was given, it was a good movie. My only qualm was the rehashing of Queen's Princes of the Universe. The song is a classic. I like Death Metal, but I didn't like the cover of POTU in this movie. I also didn't like that they gave Duncan knives near the very end but it's understandable - the destruction of his sword signifies the end of life as he knew it, as he (spoiler) was granted mortality at the end of the film.
This movie does have to be read into a little deeper than what most viewers are willing to view it as. At face value - it's an entertaining 90 minutes, but it is a little absurd (especially if you have no background with the franchise), but if you look into it deeper, read between the lines of the movie, and invest yourself into the mythology of the franchise - it begins to make a lot more sense. Or at the very least you can see where they're going with the movie. Basically, it redefines what The Prize is. Historically it was unlimited power, but this movie recreates it into mortality - the thing Duncan always really wanted throughout the series. He wanted to grow old, and now he was finally able to do it. The same cosmic force that created the immortals stripped Duncan of his immortality. The odd scene at the end showing him and Anna is pretty weird, but overall it does present a nice ending to his saga.
For Highlander fans, this movie is a must. If you are a fan but aren't willing to look for hidden meanings in some parts and characters of the film, watch it for closure if nothing else. For casual moviegoers, well, this may not be for you, unless you're looking for a reason to pass 90 minutes with an action movie, then give it a shot. If you don't care for this movie, try looking into the other. You may discover something really awesome.