Users love fast gadgets. Fast gadgets are more likely to remain installed, and will see higher usage. Fast gadgets may also cost less to keep running.
Slow gadgets make users unhappy, both with individual gadgets, and with iGoogle. Unfortunately, there hasn't been a way to tell a slow gadget from a fast one until it's been installed. To remedy this, starting in late September, the iGoogle directory will add a "slow" badge next to the entry of any gadget that's slow enough to cause speed-related user dissatisfaction.
To help you get your gadgets in top-notch shape before the badges roll out, check out our new latency tips on Google Code.