I loved it. But it's all relative really. The original Deus Ex was from a different time and came out during a very experimental phase in gaming, with many genre defining and genre breaking games coming out over several years. Deus Ex is like playing through a mind map of a developer. It tries so many things and most of it works really well.
There was never a game like Deus Ex before Deus Ex.
Human Revolution is comparatively safer. It took risks that the AAA industry of recent years are reluctant to take, but at the same time everything it did was tried and tested elsewhere. Ultimately HR feels derivative, because it is.
But that isn't a bad thing. It derived a lot of its content from other great games (including the original Deus Ex) and implemented them in a way that retains their quality while still feeling organic within the Lore of Deus Ex. The story was a lot more focused and less slapdash, which was an issue I have with the original Deus Ex. That's a double edged sword though, because the slapdash story gave way to a wacky conspiracy narrative that just fit the world, where as HR takes a far more serious tone and loses some of the franchises charm.
It messed other stuff up too. The bosses for one (which were much better in the enhanced edition... better then the original Deus Ex's bosses to some extent), were horribly done and completely at odds with the games themes. They gimped the augments with the Energy System, probably in the name of balance, but being a top end super cyborg who needs to take a break and eat a kit-kat when on the mission, is thematically and mechanically bad. At the end of the day, Deus Ex is about exploration and discovery, so handicapping your abilities as hard as they did was an awful decision and how they did it is almost comical.
But all things considered, HR was a great game. It was engaging and intriguing. The narrative felt like Dues Ex even if it felt a little less charming then the original. Combat and Stealth both worked really well (though penalties to a pure combat run felt a little harsh). Stealth in particuluar, which at the time of it's release was still a mechanic most developers avoided, worked really well... better then the original. Unlike Dishonored, ghosting the game was extremely satisfying (barring the original boss fights) and just as exciting as going in guns blazing.
Also, the Hacking in his game was done brilliantly. It turned what the original game made as a progress bar into something interactive and challenging. Kudos for making what is often very boring, very fun.