For live TV, remember, this feature also plays SLOWER than normal too, so the problem with going ahead of current isn't always an issue..
The way Tivo handles it is that if you have a buffer (which on Tivo can be up to 30 minutes live) you can put it in fast mode, and it will just play through the buffer faster. When it gets back to realtime, it just plays 1x live. I can't remember what happens if you subsequently pause again (ie: will it remember you were in fast mode) but for me, this is much less interesting than having the feature in some form. I also used to like backing up live TV and watching in slow motion temporarily (+1 for another hockey fan!!)
All of this being said, until about 10 minutes ago, I had no idea this feature even existed! I searched for it because I saw the "default playback speed" under show options on my web client.. This is something I've been meaning to ask about and was also missing, so I'm already so happy it exists!!
Last question - I have a TivoStream4k client.. Is there a way to make a more convenient way to get into this mode than to press down and go through the options menu? I am using the included remote, so my buttons are limited. I'd be curious if others are using 3rd party remotes and (for example) is there a way to map buttons to "increment speed" and "decrement speed" with one touch?
Thanks to all the devs... I've been loving Channels for the year or so that I've been using it as my primary platform. I really thought that as a Tivo user since the early Tivo 1 devices that it'd be harder, but it's been great, with most challenges arguably being me being an old dog not wanting to learn a new trick..