Strengths: GPS reception greatly improved on 201, now hardly ever losing signal under tree cover but still spooked by high-rise buildings. Enough data and screen options to satisfy even the most anal of analysis freaks (but see weaknesses below). The virtual trainer, already a superb tool, now works much smoother by virtue of the better satellite reception. The interval training function is also excellent.
Weaknesses: Battery life is shorter than the 201 at just 10-11 hours, and the low battery warning comes up early and is intrusive. Real-time pace is still unreliable. Some odd and regressive changes on the 201, eg, the mile markers no longer scroll across the virtual trainer screen. And no more "moonwalks" when I beat the virtual trainer - boo hiss!
Overall: A great gadget but still a work in progress. Many more functions, especially navigational and PC-based, than I will ever need. But still, I hardly ever go for a run without it.
Strengths: Very light and responsive, not like the usual overpronator's housebricks, great for faster running and speedwork and what I imagine racing flats to feel like. Seems to provide motion control (this flat-footed biomechanical crock has had no twinges or injuries). Unlike some other reviewers, I found the sizing to be fine.
Weaknesses: Lightness and responsiveness come at the cost of cushioning, so the Cesium feels hard underfoot during gentle plods and long slow runs.
Overall: Great shoe for faster stuff, but if you need motion control not recommended as your only pair of shoes.