I rode the High Roller once during the day and was unimpressed.  Yes, the size is there, and the ride is smooth, but there are definite problems.  For instance, you are, during the entire 30 minutes, subjected to loud, trashy music, insipid comments by a video host, and advertisements for Caesar's.  Tasteless and annoying.  There are VERY few seats in the gondola.  The box office adds $2 per ticket service fee without telling you.  There is no senior discount.  MAYBE if you buy from a machine you can avoid the service fee.  There is the usual gift shop.  Although the experience is probably better at night, the high price and the terrible music and the silly $2 service fee gouge will persuade me not to bother with an evening ride.  Overpriced and hohum unless you are drunk.  Typically Vegas?  You decide.  I say don't bother.  (But I love the London Eye.)