Showboat AC?

If you are a smoker, Showboat is the worst- the whole main floor is non-smoking.

I smoke and I don't mind but I wear a nicotine patch when i go for a day trip.
Showboat/Bally's and Caesars are the top 3 Diamond lounges- you will find 5 or 6 full courses and with carving stations- food is GOOD/ worth it to be Diamond here in AC
There is a tiny upper portion in the front by check in w/ STP and slots you can smoke- and of course the high roller area (which is large)
Diamond members get the better rooms-- you will have a coffee maker (yay!) and some marble in the bathroom.
Don't worry , valet.- it's free, so is self park for diamond.

Thanks Flip!

Regarding fees for the Diamond Clubs, Flip's already covered that (Diamond member and a guest are free, additional guest costs $25 in comps), but Harrah's will periodically cut off people who "abuse" (in their eyes) the Diamond Club privileges. For example, if I were to eat there every day without playing, sometime after a couple weeks they'd stop letting me in for free. The "fees may apply" wording was added a couple years back to give the company some leeway to keep out people who aren't gambling enough to make Gary Loveman happy.

Arrive early if you hope to get into the Bourbon Tower at Showboat. Those rooms tend to go quickly, so even if your reservation is for a "premium" room, there's a pretty good chance you'll end up in the Orleans Tower. The Orleans Tower rooms are fine, though they're farther from the casino and Boardwalk (though, closer to where you'll catch the shuttle) and the Bourbon Tower rooms have been remodeled more recently. On the other hand, the Orleans Tower rooms are newer, I think a little larger, and some (though not all) have slightly larger bathtubs.

Regarding the Harrah's shuttle, it doesn't run as often as you may like. While it is free, you may want to use other means of transportation to get around town. Your Diamond Card will get you free parking at Harrah's, Showboat, Bally's, or Caesars, so unless you're going to the south end of the Boardwalk (Atlantic City Hilton and Tropicana), you'll be able to park for free wherever else you go in town. If you go to Borgata, then use your Diamond Card to upgrade to a "Black Label" card. That will get you free parking there and most of the time they'll also give you $100 in free slot play.