I bought the metal studs from Action Gypsum in Bryan and they came in 8', 10', and 12' lengths. They talked me into using 18 gauge due to having a heavy concrete counter going on top. 20 or 25 gauge would work and be a lot easier to cut. I cut them to the needed length using a circular saw with a metal cutting blade. With the lighter gauges, tin snips probably would be sufficient. When doing the notches in the headers for the access doors, I am using tin snips and it is pretty difficult cutting the 18 gauge but it works.
During the framing process, be sure to account for all the 1/2 inches needed when adding the hardie backer board, veneer, plywood etc. This could be a real problem if it isnt compensated for. My hardie backer board will slide in front of the concrete since I do not want to see the concrete when finished. However if I was going to make it where it sits on the slab, my framing would end about 1" inside the concrete. This would allow a 1/2" hardie board and the 1/2" thick veneer to be installed and it would be flush with the concrete edge. Same considerations with the counter top heights.
Another consideration is to elevate the framing using composite decking. I would cut the composite decking in 5"x5" squares placed under the vertical studs. This will allow for water to drain under it and not sit against any of the framing. You can see the decking in this pic, however it isnt cut to the squares yet. I will also place one square in the center to support the bottom hardie board.

As far as lumber or metal goes, it is really against manufacturer suggestions to use lumber for the framing of the kitchen. There needs to be a minimum of 3' around the grill using non-combustible material. So really you could use lumber for any long runs of counter but near the grill it needs to be framed in metal. Also the lumber would not last as long as the metal studs, even pressure treated. I havent had any problems with the metal framing and would do it again in the future. However, be sure to get some C clamps, at least 2, to hold the flanges of the metal studs together. With self tapping screws, both pieces of metal need to be clamped so it holds it in place. A rivet gun would work also, but that calls for pre drilling all the holes, so I went with the low profile self tapping screws. The low profile head will help when putting the hardie backer board on and it wont have "bumps" where the screws are.
Sorry for the rambling. Just my 2 cents.