Anybody move from a keel sailboat to a Tandem Island?

I think it has more to do with available funding that you want to spend on your habit than anything else.
In our case we used to have a 24ft sea ray powerboat (about $80k), dry storage in FL is around $400/mo, and because of salt water annual maint can be anywhere between $2500 and $15k (dependent on how many motors, and stern drive units you go thru, my brother in law who still has his powerboat has gone thru two of each in the last 5yrs. Another big deal for us was the 80 gallon fuel tanks, when gas was higher we would often pay over $300 just to fill up at the marina.
Plus down here the sun is brutal, my brother in laws seats and the entire top of the boat is completely trashed from sun damage. All his seat frames and backing behind most everything are all plywood, and most of it is rotting away.
I have a friend with a 40ft sailboat, he tells be everytime he want to move it (via big rig truck) the bill is around $8-$10k.
In our case we are also RV'ers, what we do is car top our TI then use it only for day sailing wherever we happen to be. The beauty of the TI as now our only family boat is we can use for anything and everything we encounter. Obviously our TI is heavily hardened and modified so we can use it in open water.
We can one day be scuba diving 5-7 miles off key west, then two days later quietly kayaking up the Sante Fe river in northern florida (without the sails and AMA's of course). At the end of every day we go back to the air conditioned RV and sleep in comfort (just like home). All of our massive sailsets and twin outboards just bolt on as needed. If we don't need them that day we just leave them at the campsite. If we want to just kayak, the TI kayak, (no sails, ama's) is a really nice kayak (lol we even use it to do mild class 2 rapids). To date we have around 250k road miles with camper in tow and Hobies on the roof. Actually we are preparing for a 10k mile 3 month adventure starting next month. We are trying to visit as many national parks as possible (including grand canyon, and Yellowstone. We are starting out at Ft Desoto Fl (salt water, where the EC challenge starts), then off to lake hartwell ga for two weeks. Lake hartwell is 45 miles long and we need all our massive sailsets and outboards on those big lakes (our cruise speed is between 10-15mph when fully rigged). I refuse to just peddle along at 2mph, you can't get anywhere. My current range is around 100 miles per day. Which I think is great for for places like so fl and the keys (where we live), and places like lake mead, lake havasu, bull shoals, and lake hartwell, (we plan to stop at each this summer). My sister and her husband lived on Bull shoals lake, and it was a 30 minute ride at 65mph on his bass boat from his dock to the dam (a really big lake, don't try peddling that at 2-3mph (lol)).
When not using the TI it just sits in the garage on the trailer, (costs us nothing for storage or maint).
We are pretty happy with what we have.
There are RV parks every place, with many right on the water. I much prefer buying a big travel trailer with all the comforts of home, (ac, big screen TV, comfy beds, etc) for $30k, plus around $8k all in for our TI. Verses $.5 to $1 mil for a 40-60 ft live on board sail boat. We still go to far away places, last year we went to St Thomas/st John, Bahamas, Mexico, and several other Islands, but instead of try to sail there on our own, we either took cruise ships or flew (way cheaper). Around St Thomas it's pretty hostile waters), and it's not a bad idea to rent a 40-60 ft cat (with a captain and crew, pretty dangerous waters where you need local knowledge, and wouldn't risk anything smaller than 40 ft, (mostly cats in st thomas it seems, (don't know why)). Actually the Keys and Bahamas local knowledge is pretty neccessary also.
You can always tow a TI behind any of the big boats, then use it at the destination.
My vote is keep both.
FE

This is our rig at lake Hartwell last summer (best of all worlds in my opinion).


Here is a video from last years Lake Hartwell adventure, our campsite is right on the water and we just park the boat on the shore for two weeks, then go out a couple times a day.
https://www.youtube.com/watch?v=eJ9Y7gBo8-Y&t=3s
[youtube2]eJ9Y7gBo8-Y&t=3s[/youtube2]

Here is us with 6 on board last summer (yea we were overloaded)


Here is our TI, we had it moored on a mooring ball for a couple weeks at Islamarada (keys), and went out a couple time a day. (stayed in a cabin that trip (no camper). Of course we have houses in Sarasota and Key west so we just go from home, when in those areas.

I sold my Beneteau First 210, which was a truly great boat, because the maintenance and launching/hauling storage insurance etc. were about the same as for a substantial yacht, but without the full capability of a substantial yacht. The TI's added dimensions of "cycling on the water" and portability and low physical effort for cruising and fishing are big value adds. I do keep a monohull performance dinghy for pure sailing pleasure- it sails rings around the TI but is no fun for novices or long distances. I also have a 40HP 13 foot RIB that the family enjoys for tubing, swimming etc. I don't really miss the keelboat much, but if I were to get another, it would be a 33-40 footer so the hassle would be proportional to the capability.

I wouldn't move totally away from a keelboat to a TI, we really enjoy overnighting on our Watkins 27 on the lake. We also have a trailerable Santana 2023C which is a fun, light boat. However, due to our circumstances and unwillingness to continue supporting two keel sailboats, we're thinking seriously about selling the Santana and buying a Tandem Island.

Slow and comfortable cruising with the kids and grandkids on the Watkins, and the thrill of being close to the water screaming along on the TI - appears to be the best of both worlds. At 65, we still like to get wet and to still enjoy sailing when we take extended road trips would be worth getting a Hobie.