I use Unity on a daily basis. Best engine I've ever used and I've tinkered with most of them (Unreal Engine 3, Source, id Tech 3, Torque, Gamebryo, Panda and more I'm forgetting). Fantastic asset pipeline, awesome workflows, APIs and tools.
In terms of features it can sometimes be a bit behind the big boys like Unreal Engine 3 ect but it's soooooo much easier to work with and almost as powerful (rendering, physics, lighting, shadows, animations, effects ect). Half the top selling iOS games are made with Unity, it's growing in popularity on Kongerate, a fist full of steam games have been made using Unity as well as a growing number of big online games like the Battlestar Galatica MMO, Tiger Woods PGA Tour Online ect.
p.s. DICE's engine is called Frostbite 2 and it's not available for public/independent use, in terms of features it's ahead of most, probably even CryEngine 2 with it's updated tile based diffused DX11 rendering path being used for Battlefield 3 but specifics on the internals of the engine, asset pipelines and workflows are a mystery. DICE release a lot of white papers and present talks (at places like the GDC and Siggraph) about the techniques they use in their engine.
Last edited by Drac; 29th July 2011 at 08:15 PM.