REASONS TO BUY
Simple
Fun to place
Inexpensive
Great in pockets
REASONS TO AVOID
Limited applications
Walk easily unless placed in tight spots
In which case they are tricky to clean
You really have to be careful about Tricams walking. Sling them well and then still be careful about them moving about. In addition, they can be tricky to clean, especially when they are placed in a bomber and tight placement. Considering their relatively infrequent use in Yosemite, I am always surprised how many fixed ones I see on big walls. That could be because many people use a hammer with them! That's a big No No.
Tricams are ideal in pocketed areas or areas with horizontals. Gunks climbers swear by them.
When compared to a cam, they are a pretty good deal. However, when thought of as a specialty piece that will not be used much compared to a cam, they are a bit of an extra.