I visited Dollywood for spring break in 2013, and enjoyed the trip so much I returned for 2014's spring break. Dollywood is an extremely wonderful park. The theme is somewhat reminiscent of Old Virginia at KD, but each area has its own distinct country theme. I did not stay on-site at the park, nor did I check out the waterpark, but I'm happy to share what I do know.
For one thing, get in on the park's "Q2Q" system. It's the closest thing they have to a fast pass, and it's essentially a small electric pager where you can reserve your spot in line on most of the park's rides. Basically, you select a ride you want to ride and you wait the given wait time for the attraction... but you don't have to spend your time in line. Then, when it's time to ride, you and your entire party can march up the special Q2Q queue line, get your pager scanned, and enjoy the ride. So, you'll end up doing the same amount of waiting for the ride, but you have the chance to do other things while you wait. It really does end up saving you a ton of time. You only need to pay for one pager system, plus a smaller fee for each additional person who uses it. I don't typically purchase the fast pass option (I'm not Nic

), but in this case it's definitely worth it. Also, the fact that you're *technically* waiting in line just like everyone else (just not physically standing in the line) makes me feel less guilty when I zip by the "plain folk" in line.
The park's coaster collection is stellar. Most of their coasters are all located along one long strip of land, which makes navigation easy. The first coaster you come across will be Blazing Fury, which is a combination dark ride/roller coaster. Being one of the park's oldest and most outdated attractions, I personally did not like this one at all and did not ride it on my second visit. But, I would recommend trying it at least once. Tennessee Tornado is an Arrow looper, much like Anaconda, but the speed and relative smoothness make it one of my favorite Arrow loopers. FireChaser Express, the new coaster, is one of the coolest family-friendly coasters ever. The unique launching system, the scenery, the theming, the dark ride section, and the forwards/backwards element is fantastic. Wild Eagle is next: a truly amazing B&M wing coaster. Do this one a couple of times; you won't regret it. Mystery Mine is a great dark ride/dive coaster combo with some insane theming. Thunderhead is the park's wooden coaster, and with the insane speed, quick turns, crossovers, and great pacing, this one one of my all-time favorite wooden coasters. How I wish KD could get something like that...

Dollywood is fantastic at getting the perfect balance between a strong theme and a thrilling ride.
Anyway, all of the park's coasters got extremely crowded when I visited. Some of the coasters are relatively low-capacity, and others are just insanely popular (some, like the new FireChaser, are both!). The other rides didn't get insanely bad lines, but the coasters all get unbearable lines. Grab a Q2Q and spare yourself from going insane.
When I visit, the park has a "Festival of Nations" in progress, so I can't speak for the main season shows, but I hear they are very good... almost BGW caliber.
Much like BGW and KD, be sure to stop and smell the roses at Dollywood. There's a glass-blowing demonstration, different candle carvers and craftsmen, bakers, and so many other things to experience. The natural beauty of the mountainous park, from all the streams and lakes to the rolling hills and charming architecture, is unrivaled. It's funny, the park experience is very similar to BGW, but at the same time it's very different.
Also, check out some of the Dolly experiences if you get a chance. You'll have to wait a good 20 minutes or so for this, but getting to tour Dolly's retired tour bus is super cool. And the museum about Dolly's like, Chasing Rainbows, is very interesting. After realizing just how expansive the entire experience was, I started getting a little ride-antsy, but there is so much fascinating and inspiring stuff in the museum, you won't be able to appreciate the park the same if you don't visit.
There's a very clever, subtle reference to Dolly's "rags-to-riches" story in the architecture of the entire building. Let me know if you pick up on it.
The main children's area is the "Country Fair" area, with a carnival theme. There is a kiddy coaster in between the size of Taxi Jam/Great Pumpkin and Grover, a Zamperla Disk'O (one of my all-time favorite flats; not necessarily a kid's ride, though), a mini drop tower, teacups, flying elephants, etc. There are plenty of other family rides and kiddy rides throughout the park, too. Also, be sure to check out the steam train. It's a full-sized steam train, larger than the one at BGW (although the pollution it emits must be terrible), and it's so scenic; I really regretted passing it up the first visit I took.
As far as time, I would say you only need two days for the park itself to experience it in its entirety, revisit your favorites, and tackle the park at a relaxed pace. The park is comparable in size to BGW and KD, but the number of attractions is lesser. Two days should be plenty of time to experience the park completely without being rushed. You may want some extra time for the water park, but you could probably squeeze that into your second day and be fine.
Anyway, those are my little tips for the park. Hope this helps!