Beyond Compare is one of those priceless tools I pay for myself instead of waiting for my employer to pay for it. Price/functionality wise it's worth its weight in gold, it's cross platform, and its licensing is very liberal. There's just no FOSS compare tools out there that can match BC.

What are BC features that you find to be so great?

I'm genuinely curious - I heard of lot of BC being 'the tool' for diffing. I'm used to Meld, but my current employee has a pretty strict policy which tools could be used so at some point I've managed a licence for some older version of BC. But for some reason I've found its UI/the way it works a bit less optimal that I was accustomed for. Since I'm using that primarily for text diffs these day I usually use a diff tool from IntelliJ Idea (I have Idea open all the time).

In comparison, Meld is not stable, nor fast, especially for big diffs. The UI is also more limited. Araxis Merge and WinMerge are good alternatives

Yea I found Araxis Merge better than BeyondCompare, FileMerge, DiffForm, and Meld (mostly based on diffing prose rather than code, though).

Araxis Merge is ~4x the price of BC though. What does it do that makes is 4x better?

Well, whether it's worth it is going to depend both on the use case and on the user. (I figure for many folk in this thread, the difference in price is going to be pretty negligible for a tool they use ~weekly.)

For me, I eliminated BC immediately because I was often diffing prose and it didn't have word wrap; that ability is apparently available now in the beta version of BC5, but it wasn't when I was testing it. I suspect it will continue to be non-optimized for prose in how it handles long lines.