Isn't that the tail wagging the dog?!
When Firefox first started, it was built on a wonderful premise - there would be a small basic browser at the core, and then a selection of add-ons (which anybody could write) so that users could decide exactly which features they wanted in their browser.
I hate the new Tabs-On-Top design in 29, and now I'm being told that the only way to get back to the previous mode is to use an add-on.
The arrogance of the Firefox developers (you just need to look at their responses to anything criticising the new interface on the Mozilla forums, and there are reports of them deleting Facebook postings that are critical) will be their downfall.
I really don't like Google very much, and they already know FAR too much about me, but I fear that a move to Chrome may be on the way for me :-(