Basically the AI is relatively easy to beat, unless y're playin' on a map which is exceptionally hard, and you'll piss blood just to stay alive, not to mention actually defeat them. One notable map is the Cielago Depression, starting points 6 and 7. Point 6 is a tad easier as there'z a huge amount of spice rite next to you, but point 7 is next to impossible. In 90 attempts out of 100, you WILL be defeated!!!
Second one is starting point 3 in the Great Bled. The starting point is very uncomforable, and even tho it's close to spice, most of the attacks will come from there, and the AI will hunt down yer Harvesters to make you cry. Also there are tons of sandworms and they'll happily go after yer Harvesters. The entire bottom area is wide open, so enemiez can attack yer entire base at once!
Third one is the most recend, and hardest possible map, the Two Birds Rock (where Stilgar's water level went below the minimum, and Jamis shared his with him). Rock formationz here are very unfavorable and spice is very often out of reach, so you'll desperately need to invest in Carryalls. Point 2 is the most hopelessly difficult, cuz y'can get attacked by two sides and grabbing spice is damn hard, as there'z only one passage which leads to the spice field and sandworms will be munchin' on yer Harvesters quite frequently, not to mention y'actually need to share the spice with the player on Point 1. Point 3 on the X-shaped rock is a tad easier as there'z plenty of spice, but y'can get attacked from 3 directionz here. As for Point 4, it's once again a hard one, mainly because it's far away from spice fields,and unless y'move the MCV to a spice field, you'll suffer a lot getting income. Try any of these maps I made with seven AI players, they'll surely entertain you for a while if you try to win...maybe forever...