I've always kept suggestions on, partly as a FSI and partly in hopes that I'll discover some good new stuff.
Unfortunately, the feature doesn't work as I hoped it would. Instead of suggesting things I might like, it's just recording things I've already seen and rated "thumbs up."
It keeps recording the same previously rated movies over and over, instead of any of the hundreds of other similar movies available on the channels I receive. Same with series.
Those of you who have your Tivo "trained" to your satisfaction, how did you get it to suggest new things?