I think the cycler concept is a very ingenious use of some rather elegant orbital mechanics. As to its practicality, I have several issues.

1) The transit time for each leg is longer than the semi-Hohmann transfer orbit, thus the crew spends much longer time in the high radiation interplanetary environment and (potentially) in zero G.

2) The crew spends much longer times on on the martian surface. Combined with (1) this makes overal mission times very long.

3) The cycler orbit is not a perfect match for Earth and Mars, up to five cyclers are therefore required to allow a transfer each launch window. Since each cycler is a substantial spacecraft this requires substantial investment in transit infrastructure rather than on the Mars surface, infrastrucure that furthermore is only used 2/5ths of the time. This renders the claims for less mass false.

4) Launching to the cycler means a deep space rendezvous with very narrow launch windows and little margins. If a launch is delayed even minimally then I suspect that the window is missed.

5) The deep space rendezvous is very much a dock or die affair, if planet to cycler ferrys are minimalist affairs. To ensure the crew survives in the eent of a failed docking they have to be large enough to make the mission without the cycler, which makes the cycler redundant.

6) Tranfering to the cycler orbit always requires more propellant than doing directly to Mars or Earth, sometimes much more.

7) entry velocities at Earth and Mars are always higher than non cycler orbits.

So in the end using a cycler means much larger spacecraft, more propellant and greater risk to carry out essentially the same mission that a non-cycler would use.

I am sure cycler orbits are good for something, just not for travelling to and from Mars.

Jon