I'm no trapmaking expert but I know a lot of you folks have a lot of great ideas for improving the feature. Let's see 'em. From my limited experience, here are some obvious improvements.
1. Improve the cost-benefit ratio. The cost-to-benefit ratio of the traps is very, very low. This can be improved a number of ways: lower the trap part requirement, increase trap parts recovered per trap, or increase the damage of the traps.
2. Make the DC of a spell trap based on the rogue's level and/or tiers of the Mechanic PrE, NOT the scroll level.
3. Make traps recoverable once set, if not activated by a mob.
4. Remove the timer on the traps. A trap should be permanently active after it is set and not turn off after a short period of time.
5. Reconsider the use of Trap the Soul gems as a trap component. No other class skill relies on another class for its use. Additionally, one of the gems (water elemental) is so rare that it prohibits the construction of Deadly Cold Traps. As far as I know, the only way to get that gem is to use a Trap the Soul Shroud weapon in Epic Turn the Tide.
6. Dramatically increase the radius of the noisemaker trap. In its current form, it is nearly useless.