Epic's Rein and the Unreal Engine's Long Arms
Gamasutra is covering comments made by Mark Rein, of Epic Games, at the GDC London event. He had some choice words on just about everything, slamming Sony's arrogance and Intel chips, showing off Gears of War while quieting detractors, and discussing the huge number of licensees for Epic's new engine. From the article: "Rein also commented on some of the most notable third-party Unreal Engine 3 titles from this year, from Bioshock through Mass Effect, but was particularly interested in Lost Odyssey, the Hironobu Sakaguchi-created Xbox 360 RPG. 'Lost Odyssey was a little lost for a while - it took the developers a little bit of time to find out how to use Unreal Engine 3,' said Rein. He noted the problem in getting Japanese developers to change their pipeline to UE3, but that it is something developers are getting much better at."
The negative side (off the top of my head) would probably be in not knowing the engine inside and out (because company X didn't write it from the ground up.) Though I imagine in a 2 to 3 year project they could learn the engine's ins and outs.
disclaimer: I've been known to store numbers in my ass for which to dig out when quantities are required.