the reason i built mine was because i wanted it done the way I wanted. everything was put together with 2 or 3" coated deck screws, vapor barrier under the floor, etc. I drilled each hole prior to putting in the screws, and used 2 per beam vs the 1 nail they recommended. same with the floor, and roof. except the trim pieces which have finishing nails. also poured concrete footers then used the piers on top of that, will stay level .
last shed i had built i had to re-shim it to level about 5 yrs in and nails were always squeezing their way out. still, i did the whole thing, effectively, and mostly single handed, in about 40-45 hours + 10 for the concrete and sub frame. cash wise i'm in about 2200 total.