I have been on the High Roller twice now. Once with a friend at night and once during the day with my husband.
Got lucky both times, they were not crowded.
Going at night is a treat. Seeing the lights of Vegas is always beautiful against the black backdrop of the desert. The only bad thing is that the observation wheel is behind a lot of the casinos, so you can't see all the way down the strip.
I also enjoyed seeing the view during the day. Las Vegas is in a valley and on a clear day you can see the beautiful red rock formations around the city. We were also fortunate to catch the sunset.
The ride takes about 30 minutes, but that is long enough. They have a pod with an open bar that you can pay extra for, but you only have thirty minutes to slam them drinks down! Personally, I am more interested in the view.
The wheel is good to do once or twice, but not habit forming. I think it is a little pricey, but everything in Las Vegas has gone up. It is $39 for adults at night and $29 for the day without the bar. They did have a summer special for locals - Two for One Tuesdays. Check to see if they are still offering this great savings before you go.
Have fun!