I keep flip flopping on this. We are going to be in Korea for 9 days. Right now we have 5 nights planned for Seoul, 4 nights planned for Busan, with some travel time in there to get between and back to Seoul. I have thought about shaving one day off Seoul, and one off Busan. We like exploring big cities on bicycle, eating good food, checking out cool neighborhoods, unique shops, cocktail bars, etc. I understand Jeju is the polar opposite of this, which is not saying that we dislike that. A few days of nature and R+R is never a bad thing. I am just not really sure if we will enjoy it over the cities? I will not have time to rent an international drivers license, so won't have a car rental. It appears most of the things to do are just cruise around and see nice shore lines, waterfalls, etc. Also, I can't really see that there is a central place to stay which wouldn't require a car.

Anyone want to convince me one way or the other? Is Jeju worth it?

Jeju is interesting for people-watching: all the tourist sites are filled with Korean couples on honeymoon, often with a photographer in tow. But apart from that, nothing very special.

If you enjoy exploring a vibrant, eclectic urban environment you will not enjoy Jeju.

It would be pretty difficult going to Jeju without a car rental. You'll be limited in what you can see or do. I'd skip it if you can't get the driver's license. Sort of off topic, if you are set on seeing another place outside of Seoul and Busan, you should consider Gyeongju (assuming you're taking KTX between the two cities). It's along the way and is good for a couple of days' visit.

With only 9 days in Korea I would do something between Seoul and Busan (Jeonju, Gwangju, Gyeonju, etc). Jeju is ok, but if you've been to Hawaii, Mexico or really any other beachy relaxed place you'll probably be disappointed. I know we were and definitely wished we had spent our 2 days elsewhere.

Thanks very much. After reading a number of blog reviews, Jeju just didn't peak our interest too much. I have looked into Gyeongju a bit, but it appears to be all historical sites, which really isn't what interests us when we travel. Are there other things to do?

What are you looking for? If its like you previously said: exploring big cities on bicycle, eating good food, checking out cool neighborhoods, unique shops, cocktail bars, etc, it would probably be better to stick to your original itinerary. When are you heading to Korea? There might be a festival or event that might catch your eye.

I was there last April and I thought it was pretty easy to get around. The buses were nice and went pretty much everywhere on the island. Taxis were well regulated for what I saw and probably half what I would pay for a similar ride back in the States. The one thing I did find is that it's a pretty big island so you probably don't want to try and visit a lot of parts of the island on the same day. Maybe take a taxi to the first place you want to visit for the day, then visit a couple on nearby attractions by bus, and at the end of the day take the bus back. Google maps was able to route me to wherever I wanted to go by bus.

I have heard so many things about Jeju, it seems to be peaceful and natural place (even if there are many tourists) you can walk and visit some places but nothing more I guess

I did a bike trip around Jeju. It is quite doable, as it is small. For those who are used to biking it is a cinch, as people (drivers) are 99% nice (other than the one who honked at me for biking on the road, which is part of the bike path, and the bus driver who almost hit me). 3-4 days.

Everywhere along Jeju you see the coast (I guessed I biked the coastal route) and there are always cafes to get a great view (or you can go to 7-11 and save a few bucks if you want) and there are many hot springs to relax in at night. English isn't spoken much, Chinese is more useful (lots of Chinese working there).
They have good seafood, and actually I had a great burger somewhere on the east coast.