I have a set of CST C1218s on an e-bike and I ran the C740 (Nashbar rebranded) on my road bike for a short time. On the up side, the price is good and both models wear like iron. On the down side, they're heavy, not very puncture resistant, and the sidewalls are extremely stiff. In fact, the C1218s in 26" x 2.125" are so stiff that I can run them under 20 PSI (rider + bike > 200 lbs) and they're still harsh over bumps! The only way I know they need air (without gauge checking) is they get really squirmy in corners below about 25 PSI.

I continue to run the C1218s because although they're not very puncture resistant, the tread is so thick that most debris is simply not big enough to make it all the way through. On the e-bike I don't really care about the 1kg+ (each) weight (though when I do occasionally go on human power, I curse them the whole way), so I'll run them until they wear out (which may be another 5 years as tough as they wear).

I gave up on The C740s after several flats and discovering that their traction on wet roads is akin to butter on hot teflon. I relegated the C740s to trainer duty on the KK Road Machine. In that role they've been fantastic. The C740s seem impervious to the accelerated wear that plagues many road tires when used on a trainer.

Based on my experience, I would say if you care about ride quality or puncture protection or wet traction, invest a little more in a better tire. If you just need something cheap that can rack up the miles (and you're proficient at patching/changing tubes) then CST might be worth considering.