Starts out strong, but...
I freaking loved
the first few hours of this game. The humor was amazingly funny (in a juvenile way, I'll admit), the gameplay was a breath of fresh air after the endless "realistic" shooters on the market, the NP Cs
practically worshiping the ground you walked on was nice, and all in all it seemed like the wait had been well worth it, even if it wasn't the most innovative game on the market.
Then I got to the Hive.
Dark, dank, slimy nastiness everywhere, without the early-game humor to leaven it, the two girls Duke had been chasing for the entire game
dying in what seemed like an amazingly mean-spirited way, topped off by what I will admit was a fun, challenging boss fight.
The fun, while returning after I got out of the Hive, began steadily draining from there. Moving away from Vegas took most of the enjoyment out of the (not Crysis-caliber, but I can deal with that) visuals, and the Hoover Dam sequence was more of a slog than anything else, capped off with a boss fight that stopped my progress - and interest - dead in its tracks.
Don't let my disillusionment with the late game fool you: I still love the hell out of the early part. If they had kept that tone and pace up through the entire game, I'd have been perfectly satisfied. (Hm, there's an idea for a fanfic...) There were some flashes of fun in the later sections of the game (Duke Nukem's Titty City, the running Hoover Dam Battlelord boss fight, and the battle against the mook that ambushes you while you're shrunk
in particular), but they got fewer and farther between the longer the game went.
Overall, the early game is awesome, but just be ready for what you're getting into for the later part.
Addendum: I haven't tried The Doctor Who Cloned Me yet, so I can't comment on that.