I like it!

Except I'm still not crazy about the little leg of the "L" where the microwave is. I think it might be a bit crowded at that doorway.
To answer your questions:
1. Are the sides next to the fridge necessary? What do you think about not including them?
No, they are not necessary, but they are aesthetically pleasing. If you have a stainless fridge, the sides will most likely be black, so that might not be what you want to display.
2. What do you think about upgrading the legs, is it necessary? We plan on covering that area up.
No need to upgrade...actually it isn't really an upgrade, just a different style. If you're using toekick (plinth) you want to use the
AKURUM
legs because the toekick clips onto them. It won't fit on the CAPITA legs. The AKURUM legs are rated for 275 pounds per leg, or over half a ton per cabinet if you use four legs.
3. Will IKEA give us a drawing of where we'll need electricity if we tell them we're going to use their under cabinet lights? (any rec. on which lights to consider?)
No, they will not. You should consult an electrician, but make sure you've got the lights in hand when you do. Some of the lights have transformers, some don't. Some codes allow outlets in cabinets, some don't. You might want to look into the NIAN lights, they replace the bottom shelf of the cabinet and are a flourescent fixture with frosted panel. Very cool, but in limited sizes. If you are going to use lights that are mounted on the bottom of the cabinet, be sure to include some lightrail molding to conceal them.