Unfortunately your questions is a little bit like “How long is a piece of string?” It depends.
And it depends on a whole bunch of things: How large is your company; What kind of financial and sales data you want to store?
I would definitely not recommend to run the financials of a large company in Coda, and why would you? There are plenty cheap and even free accounting packages.
You will start to notice lags from a few thousand rows up in a table, depending on the kind of columns in the table and the calculations, if any. I have had a list of GL accounts totalling 4000-5000 rows. It worked, but was slow. A few seconds response time in working in that table. (The rest of the doc was not affected by it).
The thread that you referenced is a good source of information. The general discussion is valid, but the specific limitations, 2000-3000 rows and collapse is no longer applicable. In the 15-18 months I have been on the forums, I have not heard anything like that once. There has also been several upgrades geared specifically towards improving performance, and more recently the implementation of Coda 3.0 which was a major overhaul of the product.
The functionality of Coda is really in a class of its own though. There are other packages similar (Notion) or more or less similar (AirBase, Fibery). But none of them has the ease of use and feature set that Coda has.
To me that makes up for limits in size, which I have not really bumped against yet. There are many ways to address hat in your design though - annual tables for date dependent data, archiving for data with a short shelf life, etc etc.
I would like you to try a few things in Coda, ask specific questions in the forums, and get to know the product. I am very certain that you will lots if good in the product. One of the major new developments is the ability to create user developed pack. This is extending Coda functionality by leaps and bounds, and nobody knows what the future holds.
Finally, I do not think that any one tool is going to satisfy all needs. But I am doing a lot of things in Coda now, that I, as an accountant, thought I would never do in Coda and keep in spreadsheets. But it took my a year to get the Excel patterns out of my head, and really understand what Coda can do.
It is not a trivial tool.