My lower cabinets are kitchen cabinets salvaged from remodel projects with preformed formica countertops on top. I have had this setup for over 10 yrs and it works great for me, looks nice too. The base cabinets are all pressboard construction and they work fine for me. I don't think I would try to hammer form 1/4" steel with a 5lb sledge on them but for the stuff I do (old car stuff like wiring, soldering, cutting, gluing) they work great. I even have a 4" vise mounted to the countertop, over a cabinet corner of coarse. I painted all cabinet faces gray enamel and scored some orphaned overhead file cabinets designed for office cubicles to mount on the wall above the countertop. My entire investment in 16' of cabinet space is about $160 (didn't count the base cabinets cause I already had them). The overhead files were purchased used at our local Habitat for Humanity store and I got a good price on the preformed, precut countertops from HD because they had a couple of small dings on the edges.
Bud