I thought it would be useful to post an update on how my M1 is going after a month's use.
In general, it is indeed a very nice machine, and despite anything noted below I am not at all sorry to have bought it sight unseen (ordered the day after launch).
Whether it is worth the cost for someone with a newer original machine (e.g. a 2020 MacBook) I cannot say; the additional performance is noticeable, but it would depend on you use patterns.