We canned tomatoes last night. Some came from the farmers market, and some from our garden. Here's my second-timers experience (the first was the pickles, which were comparatively easy).
1) Canning takes massive amounts of counterspace. We have a big kitchen, and it seems like we used every inch. I felt overwhelmed by bowls, cutting boards, lids, cooling racks, etc, like I constantly needing to make room for something else.
2) Tomato acid burns, ouch. Or maybe I'm just a wimp.
3) While I'm on the topic of burns, it's a good thing I didn't skimp on buying canning tools. I cannot even imagine trying to do it without a jar lifter.
4) My sink is too small. This is not a new problem, but my canning pot is huge. Maybe we should fill it with the potable hose attachment we use on the fish tank?
5) I ran out of lids, another rookie mistake. Corrected by an emergency trip to the store by DH while I filled jars.
6) It seems like canning would be almost impossible without two people. Well, maybe it would be okay if you were better prepared than I was.
7) Canning is thrilling in a way I didn't really expect. I used to think it was something I'd never attempt. Not like gardening, which I had wanted to try for years. Canning seemed old-fashioned and freaked me out until very recently. But the kitchen was filled with sweet tomatoey aroma afterwards, so I think it will be worth the effort.