The Fremont Troll is a good illustration of what a quirky, eclectic, and random neighborhood Fremont is. It's not one of those sites that you will spend a great deal of time at. It's the kind of thing that is really cool to see and take a couple pictures at, then move on. Visitors to the city enjoy checking it out and it's a fun and different tourist shot from the typical ""Space Needle shot"", the ""Pike Place Market Pig-and-you shot"", and such. Its size is impressive (it's got an actual VW Beetle under one hand) and it could be fun to climb on for a few and it is just a couple blocks from Fremont's shopping, dining, and drinking district(s). Definitely check it out if you haven't already.
Pros: It's free, a great photo-op, and it's mass is overwhelming the first time.
Cons: It's about what I would expect out of Mt. Rushmore... A cool photo op, but then that's it.