In a word, it is wonderful.
You need to decide liveaboard vs. land based. Those are two different but equally great experiences. You will get more diving aboard a liveaboard due to the travel time to the dive spots... about 45 - 50 minutes each way from Koror. However, the trip out and back is great on its own, very scenic, and the resorts very comfortable. Also, it is hard to do a night dive if you are based on shore. However, some of us start going a little nuts locked in a 100 ft. hull for 5 to 10 days, and land has its advantages there.
There are a large number of dive types to suit various experience levels. We did several drift dives in fairly light current for the most part. Some sites we did not visit are reported to have high current. Reef hooks are used fairly commonly... see sticky note at top of this section. Our guides selected the dives for us based on our experience level and expected tides/currents. My sense is that all the larger dive operators are quite conservative, which is fine. There is so much amazing stuff to see in easy dives that there was no incentive to do more challenging dives.
There are some blue hole dives with great tunnels. Most of our dives were at the 40-50 ft. level with a few short deeper excursions.
There are several wrecks around, quite interesting especially if you like WWII history
I'd suggest you get Franko's dive map of Palau (
Franko's Guide Map of the Republic of Palau: Frank Nielsen: 9781601901996: Amazon.com: Books) and look it over. It gives a good sense of what is there, and is waterproof so you can take it in your dive bag.