Horses for courses; if I actually want to cook food rather than just boil water, then a trangia is stable, quiet, and works in all weathers (except possibly sub-zero temps). And for actual cooking I don't see how you could shave more than 500 grams off the weight of the UL variants, which is totally insignificant compared to my touring all-up weight. Obviously 500g here and there does add up, but as long as the rest of my kit is reasonably optimised I'm happy to make that trade-off.
I don't think my full meths based cooking setup reaches 250g...
I've had a lot of issues with meths not lighting in the cold, but then I also cycle camp in sub zero weather (-6°C this past winter was fun, frost nip, less so) So by about October, the meths setups go in the cupboard, and the multifuel stuff comes out.
In summer if I'm going somewhere I don't know what fuel I'll use, I will carry the Omnilite Ti. Nice thing about the zelph starlite stove is that it's so small I can carry it as well as the Omnilite to cover all the bases.
It's worth also noting that as soon as you are carrying any quantity of meths, the low energy density rapidly becomes an issue. Carrying the same quantity of petrol as meths, even allowing for the extra weight of a multifuel stove.
Oh, and of course, with a descent multifuel stove you get much better flame control than meths, which means you can simmer and the like.
As for the "does the weight matter?". Well my base weight is <2.5kg[1], so yes, adding an 800g cooking setup tends to smart...
J
[1] Sleeping bag (1kg), sleep mat (470g), tarp (198g), bivvi bag (484g).