All solid wood guitars have the *potential* to sound better than laminate or solid topped guitars. Since all wood construction is typically found on high end guitars, they usually do sound better. Unlike laminate, no two pieces of solid wood are exactly the same (grain, density, etc). Guitar manufacturers take great care to grade the solid wood for consistency, but there can be slight variation in tone, even on identical models. For this reason, you really should try the guitar before buying, and compare it to any others in the store. That will also answer a lot of your "is it worth it" questions. You'll be able to see and hear the quality of the guitar for yourself. You can't do that online.
Most of the guitar's tone comes from the top. That's why you see so many intermediate range guitars with solid tops. The back and sides *do* color the tone, however. That's why you see different woods being used...it's not just cosmetic. And of course, the effect is more pronounced with solid wood than laminate.
All wood guitars don't require any more maintenance than cheap guitars. They only require the same care you *should* be giving your all laminate guitar. Humidity (low or high) can cause problems with all guitars, but solid wood bodies are a little more sensitive to it. If you live in a dry climate, simply keep a humidifier in your guitar case. Guitars are happiest at 45%-55% humidity.
The short answer is that people wouldn't pay top dollar for all solid wood guitars if they weren't worth it. Try a few in person and compare to some solid topped guitars. If you can't tell the difference, it isn't worth it.....to you.