The chances of TiVo doing a software upgrade for the S1 units we've got in the UK is nearly nil. I've had a 250GB drive in my TiVo for over a year now with no problems at all. You might want a Cachecard as it doe get a bit slow when you've got a huge DB.

There is one possiblity for screwing it up and requiring you to yank the drive and copy the kernel again. There is some problem with certain TVs and teletext signalling or something along those lines and if you phone up TiVo customer services they'll push an incremental upgrade to you. There is no other reason to get the upgrade though. It doesn't add anything else.

It's only 137GB when you're using 1000 instead of 1024.