I grow F1 for:
Asparagus - grew F1 male-only variety. Should be an advantage - fatter spears and no self-seeding.
Cauliflower Candid Charm - had much better success with this than ordinary varieties (and other folk here also reported that last year)
Cucumber - F1 variety with only Female flowers - which saves a job! Also Mini Munch F1 which suits the kitchen - small fruits, harvest often, rather than a left over half-cucumber curling up in the fridge!
Sweet corn Mini-pop F1 - which the kids love. no idea if mini-cobs are available non-F1 ?
Sweetcorn Swift F1 - much sweeter, dwarf which enables them to develop cobs one leaf-joint lower, and thus be done before the end of the English Summer
Petunia Pink Orchid Mist - single colour with double flowers - which is what I particularly wanted
I am also growing F1 varieties for no particular reason where I need very few plants and the tiny number of seeds / £ doesn't matter to me, or that was the first packet I choose in the garden centre:
Aubergine Enorma F1 - no idea how it compares to others, although it is flowering much earlier than non-F1 Black Beauty
Courgette Green Bush - I think I've always grown that; never thought about F1 or not for Courgettes
Kohl Rabi - Kolibri F1 - I liked the purple colour. Grew them over-winter in the greenhouse along with some non-F1 Lanro. The Kolibri didn't make any "ball" so chucked them on the compost heap ...
Leek Carlton F1 - came free with something, germination terrible. Unless the few that I have managed to grow are amazing will stick with Mussleburgh in future - as before!
Melon Edonis F1 - can't say I notice any improvement. Lots of T&M "hype" on the packet though! Sweetheart F1 was a success last year though. The other non-F1 melon I grew last year (about 5 varieties in all) were much-of-a-much-ness
Onion Kalmat F1 - first year of growing Onions from seed - I think this packet came with John's book
am growing some non-F1 too, so I'll report back if these are dramatically better!
Radish Mooli F1 - grew very well last year, but not grown it before so no idea if the F1 variety was "better"
Squash Cobnut F1 growing for the first time, and also some non-F1 seeds from "a friend" which I grew last year and they were fantastic - be interesting to see if Cobnut is better.
Tomato Shirley - was good last year, but not sure any gain over other non-F1 Tom's I've grown.