For years the best option for us Mac-using TiVo owners to get content off of our TiVos and on to our iDevices was iTiVo. But iTiVo, built largely in AppleScript Studio, has always had a buggy user interface, and with Mountain Lion it originally required some Terminal fu to get it to work at all. Building on the work done for iTiVo (and even reading your preferences from iTiVo), cTiVo picks up and takes the whole project into Objective C, making it a faster, cleaner app than its predecessor. And as with iTiVo, cTiVo is 100% freely available and open source.
cTiVo Version 1 In Process Converting "Community"
cTiVo version 1 has been available in alpha, beta, and then release stages since December, and just last week the first beta of version 2 is out (and is the highlighted, and presumably recommended, download for it). I tested both the most recent release of v1 (cTiVo_1.3.2_206) as well as the newly-released cTiVo 2.0Beta 1 (283). The new Beta kept crashing for me, but perhaps my situation is unique. v1.3.2 worked perfectly for me on my 2011 27" iMac and the user interface is smooth and responsive. [Update 17-Apr-2013: cTiVo Beta 2 (296) solves this issue for me and I'm up and running on that now!]
cTiVo does everything you'd expect once you plug in your TiVo account's MAK (media access key). It scans your network, finds all your TiVos, and lists your shows. You set the download destination and the format (i.e. size) that you want your files in, and cTiVo takes care of the downloading, converting, saving, and it'll even sync iTunes to your iPhone when it's finished. You can also set up "subscriptions" to automatically download new episodes of any show you regularly watch. And hey, it's free — what more do you need? Go get it!
cTiVo requires OS X 10.8 Mountain Lion or 10.7 Lion and is not (yet?) compatible with anything earlier than Lion.
Reminder: You can bypass Gatekeeper by Option-Clicking on an App and choosing "Open"
A reminder to Mountain Lion users: this app is NOT signed, so your default Gatekeeper preferences will likely prohibit you from running it the first time. To bypass this, simply right-click on it and choose "Open" — you'll then be able to agree to let it run and future attempts should sail through, uninterrupted.