They're pretty cool! Here's a table of roughly how fast you would go compared to on a normal bike:
| Description | Power | Speed (velomobile) | Speed (normal bike) |
| High effort | 400W | 107 km/h | 28 km/h |
| Cruising (jogging equivalent) | 200W | 85 km/h | 22 km/h |
| Almost no effort (walking equivalent) | 60W | 57 km/h | 15 km/h |
I got these numbers by starting from the Quest velomobile top speed of 107km/h with a high-performance rider and projecting down, and the normal bike speeds from the wikipedia page, projecting up (they match my normal riding patterns pretty well).
You can do your own projections using the following equation (change the initial speed and power ratios as appropriate):
15 km/h * ((400W / 60W)^(1 / 3)) = 28 kilometers per hour
