I’ve been using Diarly seriously for about 18 months in total. I have over ten years and a dozen journals in it imported without problem a while ago from Day One. I have a daily journal used every single day and the others are for particular purposes (e.g. piano practice and learning, quarterly review, a holiday in California)
It took me a little while to set the editor (font, size, line length) etc. to preferences that work for me and a while longer to set the prompts I wanted in some journals (e.g. a weekly review journal) as there has to be some trial and error, but I now don’t think about Diarly at all: just about what I want to write. The sync is rock solid and fast for me and I use the encryption it provides - it took quite a while to do the initial sync to encrypt but it works fast and smooth now between my Mac, iPhone and iPad. I occasionally dictate from my watch too.
It looks and feels a bit less polished than Day One, but I can’t say I have ever missed anything from that app and I haven’t had the niggling issues (e.g. weather disappearing, web access suddenly being added) that I had with Day One. Development is still active and the developer responsive. Give it a try.
I use it sporadically. I, too, moved from Day One. I gave up Day One after realizing I was wasting my money (journaling is one of those things I always think I should do, but I always re-discover that it’s just not my thing). I occasionally get on a spurt and use it for a week or so, usually for ski trips to memorize things or remember tips/tricks I pick up, and then stop using it. So for that limited purpose, I’ve noticed no difference between Diarly and Day One, except for when I used an IFTTT recipe to save my social media likes and posts to Day One. I’ve lost the ability to do that.