I'm not married myself, but have lots of sisters, cousins and friends who are. Most have done their own invitiations, and they've turned out very nicely.
One of my sisters, as well as my best friend, both used invitation kits that they got at Staples. There are a lot of really neat designs available to suit a variety of styles/themes. Another friend got paper from a scrapbooking store, cut it to size with a rotary paper cutter, and did really pretty layered invites.
I helped put together the invites for each of them, and it's not difficult, but it is pretty time-consuming. The advantage is that, depending on how much time/effort/money you're willing to put into them, you can get precisely what you want. But my advice would be that, if you don't have family/friends available and willing to help put the invites together, try to either stick with a simple kit design, or just have them done professionally. You're going to be busy enough.