I have a Diamondback Wildwood, and in a lot of ways I love it. It's very comfy to ride, it's super-stable and handles great, and it's just fun. I've been riding frequently since ... around the beginning of April, I think? My comfort level on the street and my willingness to go farther afield have dramatically increased.
But my neighborhood is super-hilly; everywhere I go is on at least a slight grade, usually much more than a slight one, and I'm generally going dowhill on the way out, and all uphill on the way back when I'm carrying more stuff and have already been riding a few miles. The elevation gains are still kicking my butt! I know that I've gained in fitness and stamina, but it's not paying off in being able to breeze through that last half-mile to mile of climbs to get home, especially when I've got a full load of groceries onboard.
How much of this is me being a big wuss, and how much is due to riding a big heavy upright bike? It does have 21 gears, although I can't say that dropping to the low gears in the front seems to help too much; it mostly just makes me reaaalllly slow without making my perceived effort that much lower. I do think that I tend to push too hard on upgrades, because when I ride them with 10-year-old and go super-slow, they feel more or less effortless; but by myself I'm hyper-conscious of going slow with cars behind me ... even when I consciously tell myself to take it easy, I seem to be pushing too hard.
I really don't want a super-aggressive bike -- I love being able to look over my shoulder easily, and I enjoy being upright. But I'd be willing to upgrade to a better bike, and maybe one with slightly more efficient geometry (I'm intrigued by the Trek Allant) if it would give me more power uphill. I'd like to start doing 10-mile rides instead of five-mile ones and run errands farther afield, but I'm not sure I can struggle up five miles uphill on the way home ...