Joins are coming very very soon. Stay tuned.
I've just given it another go with Airbyte Cloud and I think some of the issues I had have been fixed (I remember back when I tested it was pretty clunky to select tables to sync with hundreds of custom tables) because I didn't have any major problems.
One thing that is a showstopper that is probably very specific to my use case is it doesn't allow you to filter tables before syncing, my client has offices worldwide but I mostly work within a couple regions so some of the tables I want to sync I would like to put a filter on as they have a "Market" custom field for the country.
I can of course just sync everything and then filter on the destination but as a consultant I'm wary to sync data that I have no business working with, plus it would increase the data size of the sync massively.
Overall I do love airbyte though! it's a great tool, and I use it for other data sources, just didn't work for me in this specific case
EDIT: I just noticed I was unnnecessarily harsh in the parent comment, I was more thinking about other tools that have very basic SFDC integration (only standard tables, no custom tables/fields) – airbyte's integration is overall good, it just didn't work for my specific usecase
I loaded in around 100k rows and performance was fantastic.
I think the only feature so far I haven't found is whether there is a way to join tables together in the app. With SFDC particularly it doesn't seem to have an option to write the SOQL query directly, and I can't access relationships with the field builder, so I have no easy way to do a client side join (apart from a ton of VLOOKUPs which is not ideal)
I do love how calculated columns stay even after I re-query the source data, that and the auto-expanding are killer features.
Super exciting product, very polished, I can't wait to see where it goes.