I'll post the
OverKill-Trailer reply: We have a 2575RL with 5.0L Mercury I/O (tritoon). Big boat. Heavy Boat, especially when loaded up including 61 gal. of gas. I bought it used from my Sister-in-Law, so we had to get a trailer. We don't live on a lake, so it will be trailered 100% of the time, and the closest lake we'll go to is 1 hr. away. I wouldn't be surprised if we put 2000 miles or more per year on the boat trailer with repeated load/unload up/down boat ramps. I took to heart what I read in the Midamerica website about the difference frame structure and strength makes in trailer durability. Lots of good common-sense info on that website.
We also have a 30 ft Airstream with twin axles (8,000 lbs, 32' LOA), so we are familiar with pulling moderately large rigs, and we've learned we don't like trailer sway
AT ALL (especially when my co-pilot is driving)!
So, I researched trailers a lot.
Manufacturer: Decided to get the Midamerica Heavy Duty. The Midamerica website had so much good common-sense info that I decided I could trust them - and, its one of the favorites on this forum also. Heavy duty is probably overkill for smaller boats, and for those who don't trailer far.
Wheels: I upgraded to 14" wheels. I don't like little wheels on trailers because common sense just tells you its a bad idea for long high-speed trips in hot weather. In the picture of the Airstream below, those are 14' rims with Goodyear Marathon trailer tires which I've since upgraded to 16' rims with Michelin truck tires.
Axles: I got triple axle in the hope of reducing trailer sway - we have a $3k Hensley anti-sway hitch on the Airstream that works wonders, but those won't work on a boat trailer with compression brakes. While I've only towed this boat about 500 miles so far, most of that was on highways and I can definitely say that there is absolutely no sway issue with this rig when big trucks pass us. Is it because of the triple axles? I don't know for sure. The third axle may be a little bit of overkill for this boat, and would definitely be so for smaller boats - but I'm really glad I have it given the relatively small incremental cost.
Brakes: I have disc brakes on four of the six wheels. Years ago, I converted the Airstream from magnetic drum to electric/hydraulic disc and feel much safer (especially going over 12,000 ft mountain passes!). Disc brakes is the only way to go if you're going to be travelling far and fast.
Ladder: if you will be towing most of the time, a ladder is a must, as mentioned by H2GO. Its the only way to get into the boat, unless you want to carry around a big step ladder!
Compression Hitch Coupler: I strongly recommend the electronic lock-out for backing up (5-pin hookup). Otherwise, you'll be constantly jumping in and out of your truck to install the brake lock-out key for when you are backing up.
Loading Guides: I'm new to loading/unloading a boat onto a trailer. For the very first loading on the trailer, the four guides weren't yet installed (see pics below) and I struggled to get the boat onto the trailer in calm water and a moderate side-wind. I don't know how much of that effort was due to being a newbie, but now that I've installed the guides, it seems to be a lot easier even under more difficult wind/wave situations.
Tow Vehicle: We tow with a 5.0L F150 4x4. I wouldn't use anything smaller on a rig this size. Having an appropriately sized tow vehicle will definitely impact your towing experience. As we say on the Airstream user forum, you can tow the biggest Airstream with a VW Beetle... but stopping it or controlling will be a problem!
Some other interesting info: With the boat loaded and the stern drive in trailer configuration, the rig is 36' exactly from ball to prop (my Chief Mate is wondering why she should be towing the boat when I'm towing the (shorter) Airstream....). I've also noticed that the boat tows really differently than the Airstream. The Airstream double-axles are about 60% of the way back from the hitch, while the boat axles are 75-80% of the way back. This results in the boat turning much more inside the truck than the Airstream does, so we have to swing wide and take two lanes to turn - more like 18-wheelers - otherwise we clip curbs, stop signs, pedestrian's toes, etc.
Regrets: I wish I had gotten the galvanized version, although its a lot more expensive. Maybe a couple of times per year we hope to launch in saltwater or brackish water south of Houston, and I like my equipment pristine, so I'm worried about corrosion.

Any comments from folks who know more about this than I do?
It seems to me that most of the folks on this forum don't tow very far, often to the same lake or marina, and often just in spring and fall. As it points out on the Midamerica site, they can get away with a much less expensive trailer. The one I got cost $5250, but that's a fraction of the value of the boat its carrying!

This is my Chief Mate... she's my Co-Pilot when we're driving the Airstream!

Just delivered last fall... guides not yet installed

Just to highlight the axle location I mentioned above...