It's not the frequency of updates that concerns me, but the numbering of them. It's not so long ago we were all using Firefox 3.6 and wondering whether to upgrade to Firefox 4, and now we seem to have hit some sort of [numeric turbo-boost] up to version 13 and soon 14 and [17 or 18] by the end of the year.
We're left wondering what the number actually means. Mozilla have switched Firefox from a [change-significance] release number, to what seems to indicate that each successive release is a major change from the previous one. Whether the changes from [Firefox 12 to 13] warrant a major release number increment, well the changes sound a lot like incorporations of existing Firefox add-ons and utilities into the main package ([new tab/often-used sites])([load tabs progressively])([profile manager]).
["Rapid Release"] (as Mozilla are now calling their change/upgrade process), seems to be a very good idea. Though in a desktop lock-down/corporate environment I'd guess sysadmins would want to push through updates on their own timeframe (every quarter?) and wouldn't have automatic updates enabled for either Firefox or Chrome.
I'd have preferred it if Mozilla had switched Firefox to a [Ubuntu-like numbering system], using the major number as the release-year and the minor number as the release-month. That would've made a lot more sense to me, though maybe I'm a dinosaur in this, and that in a ["release early and release often"] environment, the [version number should be meaningless]. Roll-on version 99 - maybe it will [come with a Flake].