M.S.
for my kids it was a texture thing. neither one ever ate stage 3 foods.....anyway, by 2 they were given a choice - veggies like everyone else or did they want it in the baby food grinder (which, ironically we never used when they were infants). if they chose the grinder, they had to have one bite in their mouths not ground up and chew it (but could spit it out) and then an appropriate sized serving ground up (pureeing would work too). I think my youngest was right at her 4th birthday the last time we gave her pureed/ground veggies. she still doesn't like the texture of some (apple slices, raw carrots and the tops of broccoli in particular) but can choke them down. I can't blame her - I still won't eat raw cauliflower because the texture just makes me gag!
by giving them the choice of ground or whole, it gave them a measure of control and really eliminated most battles. It also kept them used to the taste of veggies so when they were able to stand the "normal" texture, the taste was ok.
we also have a rule of no seconds until you've eaten most of what's on your plate. we'd give a very small serving of whatever they like (i.e., pasta) and there was no more 'til veggies were gone.
each kid also gets one thing we don't make them eat. one kid refuses tomatoes (slices or cherry tomatoes). the other refuses raw sweet peppers.
my other trick works from 3 to 3 1/2 years old and up. the kids get to pick one fruit or veggie I would not normally buy when we're at the grocery store. 3 bites must go into their tummies (presuming the adults can choke it down) or they don't get to choose something the next time.
there's nothing wrong with hiding veggies (I do it w/my husband but not my kids!). but its important to accustom them to veggies straight as well.