This is an optimization issue. Orion appears to be hogging 1 core at 100% when downloading anything. The speeds are around 20MB/s, and there's nothing special about the "delivery" of the download or whatever, it's a direct download. More than 1 downloads make all pages of the browser insanely laggy. I have no extensions installed.
Keep in mind this is on the brand new 16-Inch MacBook Pro (2024).
I expect these optimizations to be added in the first release, or hopefully ASAP. Neither Firefox or Chrome have this issue.
0.99.130.2-beta (WebKit 621.1.2.111.4)/Mac 15.2 (Build 24C101)
Sequoia (15)