The random spell mechanic is worth the price of the encounter. Just played this with a group of nine 3rd level charaters. Added this to another self created side adventure to create a full day (5hours) of gaming and one larger adventure with the random spell mechanic going throughout it all.
Players were mostly 10-13 in age (two dads brought their kids together for a much requested combined adventure). Once the group figured out that magic could be random and that a magic missle spell could turn into Lightening Bolt (true story) or Mirror Image the Yeti (also true) they really got into using magic and seeing what could possibly happen next. For the young at heart who like the "let's make this interesting" approach, they got a kick. And of course, a Pink Yeti makes it memoriable.
Suggestion for Publisher: The get more help start was ackward and didn't work for us. Had the random effects of round one search apply to round one of combat. Feels like there needs to be a different hook to get a group to get the extra help.