DH did the basement in our old house. We were very happy. First, he gutted it down to the cement (it had previously been finished, but had water damage we knew about when we bought the house, so we wanted everything out). He then leveled the cement floor, re-did the plumbing to move the bathroom - we did have a contractor in to re-do the duct work we wanted move and to lay down the natural gas lines we wanted. Otherwise, DH did all the plumbing, electrical, etc. We put in a tile floor, 3/4 bathroom, lanudry room, wet bar, gas fireplace, home theater, etc. We also put in new hardwood stairs to the basement. All the wood, trim, doors, cabinets were bought unfinished, and DH stained everything to match.
Overall, it did take DH quite a bit of time, but we were very happy with the results.
I think one of the issues to sort out ahead would be any concerns around permits, etc. - What is required in the area you live, and what inspections will be required. There were certain things we had to have licenced contractors come in and "sign-off" on to meet the permit requirements, but all worked out.