I have climbed extensively in Arkansas, but not at Horshoe which can be crowded and does not reflect climbing in Arkansas as a whole. A trip to Arkansas without climbing at Sam's Throne would be like a trip to NH without visiting Cathedral. Sam's also has a bunch of surrounding areas, bluff lines that go on for miles and miles.
Mt. Magazine is a worthwhile visit, the highest point in the state. Arkansas' stiffest grades are found here. Jamestown is a great backwoodsy sport crag not to be missed, especially at the more moderate range.
Sam's, the Mag, Jamestown all have free camping. Jamestown has 3 a.m. redneck entertainment, that's free too. Bring food to any of these areas, resupply isn't what we're used to in the northeast. Bring a rack to a number 4, the trad is awesome and sometimes a wide piece can help. PM me win questions.
The new guidebook is awesome and accurate and should be acquired.