Don't call it a come back. UT's been here for years...
To get it out of the way, they did improve it, though given their efforts in other Epic-made games (Gears of War, namely), and other games using their engine (Bioshock), they still have a long way to go to making an Unreal title with quality story telling.
But who am I kidding? Those on this site reading this won't even care, and some may not ever play the campaign at all. But for those that are interested, you play this soldier guy who used to have to worry about dying, and nearly avoided getting killed by some Necris chick. So now he's been enlisted by Izanagi where he meets a UT vet (Malcolm) and starts to learn what it's like to work with newer deathmatch technology, and using his job as a way to get back at the Necris for the slaughter he'd nearly been a statistic of.
Obviously, there are parts of the story that feel a bit forced, like coming up with an acronym for the flags... but all in all, it's good filler, and good practice for the online if you decide to turn up the difficulty proper.
One thing that Unreal has always been famous for is being able to bring deliciously pretty graphics with an engine that can also do it quickly, with great scalability even on lower-end systems. That being said, you really get your money's worth here with a system that can have the details cranked to max. Anyone that says otherwise needs their eyes checked.
Using onboard sound, the audio does its job and there's a good bit of surround sound going on. Though if I'm honest, this title is motivating me to look for a dedicated sound card again.
Speaking of upgrades, there is good news for those that were thinking about or have an Ageia PhysX card. Even on the stock maps, UT3 sees a measurable improvement in performance for those equipped with the PhysX hardware. Granted though, the largest improvements happen either in more heavily loaded maps (i.e. greater than 16 players), and especially on the AGEIA-made maps that were designed with the PPU silicon in mind. As a side bonus, it at least does indicate that future games that use this engine (Gears of War, IIRC) will also see an improvement.
Compared to most computer games, and particularly earlier iterations of UT, UT3's menu system feels a bit awkward. My first guess is that they decided on this as common ground to work with when porting the game to the PlayStation3 (and upcoming Xbox 360 release), but it doesn't feel like you can find everything where it's supposed to be as quickly with the new interface. Still, though...
Many of the old favorites come back. Pretty much all have been redone to look prettier/more detailed, and some feel retweaked. The rocket launcher's firing methods are more accessible, the BioRifle has a more visible charge, and the minigun's alt-fire in this iteration feels much more unique than what it used to be in UT99 for example.
Obviously, one of the reasons to release a new UT is to introduce new game modes. New (to me) is Warfare, which allows controlling of check points to open up the enemy core, and optional points that grant certain bonuses to make a difference. Obviously, the bigger difference-makers come in maps that let you access say the only flying craft, or the Leviathan (and basically skewer their power core well before they can weaken your armor enough to start worrying).
Speaking of the leviathan, it leads me to talk about the ally A.I. in particular. They sure don't have a problem hunting down each other, but when it comes to actually doing certain objective-related stuff or anything other than hunting each other down, they seem rather brain dead on the matter. It's a bit annoying to hear one of my allies mention how we should all "jump into the leviathan" and basically be a rolling death kr3w, but then nobody actually does. Or when a couple of allies are standing right next to me with link guns whilst I'm in a tank and I don't get at least one repairing me whilst I employ my superior firepower. It would be nice if they'd at least employed a little more tact, but I have to wonder if it's depending on what difficulty I'm playing...?
Nevertheless, the game gets credit on many of its technical merits - it's silky smooth, it's **** beautiful, and manages to remain brutally fast while doing so.
As an evolution of the series, it does its job and helps make up for the awkwardness that were UT03 and UT04. As an entry to try and redefine the genre and evolve the first-person-shooter, not so much. But you'd be a fool to ignore its presence. And an even bigger fool not to get this game if you've got a system equipped with a PPU (ideally, an OpenAL sound card, too).