Road Fan, I was going through this thread and noticed that I had overlooked a couple posts.
You asked about what "criterium" frame geometry is. You seem to have a rather small frame size (53cm=20"), and this is borderline closest to the smallest one can go before having to extend the top tube because otherwise the downtube would intersect with it... I'm not confident my answer will apply to the smaller frame sizes, but I can comment on more "average" frames such as the more common 22"-24" range:

Criterium bikes are designed for smooth to average roads/pavement, fast turning with hard acceleration coming out corners.

3 areas of frame design have been optimized for the criterium type of riding:

1. more "aggressive" angles - steeper head and seat tube angles
2. shortest wheelbase possible: shorter chainstays, so that the rear tire almost touches the seat tube (2-6 millimetre clearance), approximate length 39cm. Shorter top tube, with a longer stem to compensate depending on a particular rider's reach (this was good for me as I am longer in the legs as compared to the average a man) - but careful, a shorter top tube also brings the front wheel closer under the rider and increases risks of flying over the handlebars during emergency braking)
3. some will also have a slightly higher bottom bracket, to allow for pedaling through some of the tight corners at speed

I believe that my Cambio Rino had a criterium geometry. It was a brazed steel frame, made of a mix of Columbus SL and Columbus SP with semi-sloping cast Columbus fork crown. 18.x lbs back in the mid 80's was rather remarkable for $800 back then! ($1800 Colnagos and other pro bikes with their campy super-record components weighed in at 21 lbs at the time - no $10k bikes back then... $2k was pretty much the upper limit in those days when there were only millionaires, no billionaires on this earth... how things have changed). Despite the criterium geometry, I went on 100-150 km rides daily with it (60-100 miles).

Take note that when talking ergonomics, I am more or less a believer in importance of seat tube angle for rider positioning, because you can adjust the seat's fore-aft position to change the effective angle. From an ergonomics standpoint, what the seat tube angle DOES in the quadrilateral (YES, quadrilateral with the head tube of any bike 22" fame size and up being the 4th side) is affect dampening of road surface caused vibration and effective perceived comfort of the bike, and from a geometry point of view (and this is more important) as to how close you can bring in the back wheel (thus your chainstay length and ultimately the minimum wheelbase you can attain). But my point of view is that it's not so important for rider positioning, because you can get seatposts with a different offset and you can adjust your seat's position too.