The questions
1. Is waking up at the optimal time (light sleep before alarm) shown to reduce daytime grogginess rather than just wake-time grogginess?
2. Is the continued waking up at the optimal time free of any adverse effects in the long run ? I did some googling to find answers to the above, but couldn't find anything layman readable or substantial. If I have to pay $60 for a product, it is really a pain to do the research myself.
Some excerpts
"subjects were presented a word list 1 min after arousal from different sleep stage ..."
"The most important finding from this study is that sleep inertia reduces decision‐making performance for at least 30 min."
If it makes me feel good just after waking up for an hour or so, then is it really that useful?
(Edit: Read the second pdf)