Why, Mozilla, why?
I mean, I suppose there's a certain logic to the new method, but you're asking me to unlearn a habit (looking to the far right for new tabs) that's been ingrained for years. What's more, you forced this on me without asking, and without giving me an option to revert to the old way.
(That's Microsoft behavior! Did they buy Mozilla when we weren't looking? I kid, I kid.)
If you want to turn back the clock on Firefox's new-tab behavior, you can--but it takes a little doing.
1. In the Firefox address bar, type about: config, then press Enter.