There's also the other side of the coin: living 20 years in a day may be hard on the body, even if you don't have time to actually grow a Rip van Winkle beard. The brain does still have to go through the biochemical acrobatics of experiencing two decades' worth of thoughts. Perhaps Chief O'Brien would indeed have died peacefully in his bed at 140, surrounded by loved ones, but will now have to settle for dying at 120?
While these are compelling caveats, I would expect that this type of life experience would be gentler. The person would still breath and have their heart beat at their normal rate, not at the accelerated rate. The brain would not need to direct motion or growth. Indeed, the brain would only be busier with conscious thought, which is probably only a small fraction of its activity.
I am surprised that there wouldn't be any life development benefit. Picard was able to pick up a musical instrument during his alternative lifetime. He wasn't great at it, if evidenced by his attempt to record classical music, but still had a good knowledge of music thereafter. I suspect that he would just need to develop the muscle memory in order to bring his body up to speed with his mind. I imagine that an individual might learn languages, philosophy, basic engineering, etc.
There would then be the possibility of compressing a lot of thought work. Perhaps the months or years it might take to write a manuscript might be reduced by allowing the individual to accelerate the thought work. Let's say someone wants to write about Vulcan politics. After they've done the research, they use the technology in order to brainstorm the writing. In the space of a minute, they could do months of thinking things over, perhaps not needing to stop for sleep, food or recreation during that time. Once they awaken, they can proceed with writing.