I have a saw like that, a Makita LC1230. I have also been wondering about the cutting speed - 20 m/s to me sounds more like a grinder than a saw. Then again I don't do much metalworking.
I haven't used the saw much, so I can't give any reliable advice on blade longevity. It does cut solid bar, albeit noisily and with much vibration. (The universal motor does not help the noise.) The cuts are generally smooth and straight yet with visible saw marks. On most cuts the blade will push the last part of the cut downwards to form a burr. The saw lacks a stop to set cut length. Here are some materials I've tried:
Square tubing, 5 mm thick, 70x70 mm section, mild steel
With the standard blade. (Makita A-86723, 305x2.4x25.4 mm, 60 teeth.) 20 seconds a cut. Works fine.
Square 3/4 " mild steel bar
With a replacement steel cutting blade. (Makita B-09765, 305x2.1x25.4 mm, 60 teeth, 0° rake.) 10 seconds a cut. Works fine.
Ø 50 mm EN 1.4418, S165M, X4CrNiMo16-5-1 stainless
With a cermet tipped blade. (CMT 226.580.12, 305x?x25.4, 80 teeth.) CMT offers better pricing than Makita. 20 seconds per cut. I'm not sure the blade would last long cutting these.
Ø 100 mm aluminium 6082-T6
With the standard blade. Maybe 120 seconds per cut. Cut fine halfway through, then started gumming up. Would be better with some sort of coolant, or cut from multiple sides. I'd say the saw is too flimsy for this size stock.
Ø 52 mm SS2244-05 / 42CRMO4
With the standard blade. 20 seconds per cut. Chips come off glowing and turn black after cooling. New blade dull after 3 cuts. Fourth cut behaved like i was using an abrasive saw. Terrible idea on my part. I'm not sure about the temper on the stock I cut - a fresh HSS drill dulled after about 100 mm total in this material.
I also have a blade intended for aluminium (Makita B-09684, 305x2.4x30 mm, 100 teeth, -5° rake.), but I haven't used it yet. Do tell if you'd like to know how it performs.
I'd say the saw is good for tubing, okay for smaller diameter soft material (say up to Ø 50 mm aluminium and mild steel) and pretty bad for larger stock and harder materials. For larger size stock, I recon a saw blade like this mounted on a motor on an XZ slide (so as only to cut a portion of the stock per pass) would work well. 1400 rpm is just right for an induction motor.
As Clive mentions, the vices on these saws will make your Schaublin cry.