The effect does not seem likely to be very strong to me. What we would need for this to be a problem is serious long-term delays in progress. A few short term delays would actually be acceptable in this context.

Consider that:

• Most potential test subjects lives are currently being wasted. Disease progression and death does not happen on a set schedule, and we only have data and brainpower to support a limited number of experiments anyway. This would give us a high precision control over the death and dying process, making it easier to study.
• There is still a pretty good chance of getting volunteers, since it would be a very meaningful way to go. And further, patients who "die" could be given high quality cryonics, or reversibly suspended during the terminal phase of their disease progression. They could then await either em conversion or much better therapies.
• With more time available to patients who need it, less risky trials with lower chances of loss of life could be justifiably used. This could perhaps delay the science, but at a reduced direct human death toll.
• Reducing the direct political pressure for immediate results on hard to measure outcomes could actually result in less bad data and thus produce faster progress in the long term. The political pressure would be more for accurate data that does not get refuted in the long run.

There are a lot of hidden benefits and costs to be considered.

Would healthy people use it, like the comic suggests? If so, would it be a net negative or a net positive?

It is not clear to me that even STEM people using this on an individual basis is a bad thing for progress -- e.g. some might use it to get past phases of cultural boredom that would otherwise trigger a counterproductive binge of video gaming or scientific crankery. In fact, it might remove counterproductive cranks at a higher rate than productive rationalists, because they (presumably) have lower satisfaction with their current lives.

The worst hidden costs I see are essentially apathy and inertia related. If you can "fix" the problem by putting it in a freezer, you haven't really fixed it yet. Say we use this on homelessness/joblessness/insurancelessness. Huge potential economic savings there -- but then where's the motive to take people out of the freezer? Perhaps as a sanity measure it should be required that healthy individuals be brought out every 4 years or so to participate in the political process.