I've been meaning to review this game for over a week now, and as soon as I have time to read more of it I'll do so. In the meantime, definitely check out this link to the FREE download. Yep, the full PDF of the core game is completely free. You wouldn't be able to tell it from the quality of the product (as well as its design).
From what I've read so far, Radiance is largely a streamlined mix of 3rd and 4th edition D&D, heavy on the 3rd in design and presentation. In my opinion it's a much better product than either 3rd edition or Pathfinder, however. It's not quite so simulationist, and the math and balance are both a LOT cleaner. There are a ton of races and classes, and other selling points include no feats and no spell lists. Everything comes from class features, and there are plenty of options within each class for customization. The presentation is very sleek and concise, however, so it looks very easy to run overall.
The assumed fluff is also quite interesting; this ain't no generic fantasy world. It has a Victorian-era feel but with magic, elves, etc. And "electro-tech." Kind of steampunk, but not quite. Classic fantasy Fighters and Wizards mingle with Gunslingers and Medicants (both core classes). You know what else are (basically) core classes? Vampires and Werewolves (under the name Dhampir and Shifter). There's perhaps too much to work with as it's a bit overwhelming, but better to provide the crunch and have most groups cut out what they don't want, right?
Anyways, check it out for yourself. It's free, why not?