So, I've had my Sea Eagle 380X (new version with the 16 drain valves 38lbs) for about 2 weeks now and I've had the opportunity to get it out on flat water, open water and white water so I thought it was time to share my thoughts.
I give the 380X a 9 rating but that really should be a *9. The asterisk is because this is marketed as an all water, versatile kayak and it is... it's just not equally good on all types of water.
First, where the 380x shines, white water. This is what the kayak was really designed for and it does it well. With the skeg removed this boat is very turny and for white water paddling that is a good thing. It will go straight if you use good technique but when you need to turn you can do it on a dime. It rides nicely over waves and when water does enter the boat it drains quickly out of the 16 self draining ports. Also, the drop stitch floor can be inflated to a very high pressure (14psi) and that makes the boat very rigid. The only down side, and the reason for 9 rather than 10 stars, is a significant amount of water does enter the boat through the drain valves when they are open. This adds mass to the boat and while I didn't really notice any difference in turning, it can sap some of your burst, not a great thing for white water. This can be mitigated somewhat by making sure the floor (it's removable) is strapped down tight and the pontoons are properly inflated as that will help reduce the water intake. On the plus side, I've found that if the floor is inflated to at least 4 psi I am not sitting in a puddle of water like on a kayak with an I-beam floor (I'm 6'6", 230 lbs) I have seen a few reviews that complain about getting wet when the valves are open and I honestly don't quite know how to respond to that. If you are paddling white water you ARE going to get wet, if you are doing it in a SOT kayak water IS going to enter your boat so... If you are not on white water closing the valves keeps the boat high and dry which brings me to the next section.
Flat water paddling in the 380x isn't actually too bad, as far as inflatable kayaks go. Assuming we are talking about a somewhat protected, deep river for example, you just put the skeg in and the kayak tracks as well, or better, than any hard shell SOT I've ever paddled. It's not even all that slow. It isn't keeping up with a hard shell sea kayak, or even a skin on frame, but as far as inflatables go it isn't terrible. However, it has very little glide which means to maintain your forward progress you have to maintain a moderate frequency on your stroke, there will be no mini-breaks in this boat. I give it a 7 for good tracking and reasonable speed.
On open water the big pontoons start to become your enemy. Wind is not fun to deal with in the kayak, and while that is true on any water craft it is especially true of the inflatable kayak. The skeg will keep you tracking straight, even in relatively high winds but you will notice the wind is going to push you quite a bit. On the plus side the boat is very stable, handles swells and waves very well and is actually pretty fun in a surf zone. Still, if you are primarily looking for a boat for open water and are insisting on an inflatable rather than a folder, then you might want to check out the Sea eagle fast tracks or the Razorlites they are supposed to be decent on flat and open water (can't say, I've never paddled them). As far as the 380x goes, I give it a 5 for open water just because it will easily ride out most water conditions, but plan some extra time in getting to your destination.
Okay, those were the specifics for various water types. In general the 380x is highly stable, the drop stitch floor gives the kayak tremendous rigidity (more so than any other inflatable, some of them quite a bit more expensive, that I've paddled), it tracks very well with the skeg in, it is easily manageable solo but can be used tandem (it's going to be a bit cramped for taller paddles in a tandem configuration though), more than enough room and weight capacity to carry all your gear for an extended trip. It's tough, you aren't likely to puncture it on anything that wouldn't hole or crack a hard shell but if you do manage to puncture it, field repairs are easy (certainly easier than a hard shell). It is easy to set up, fits in the trunk of even a small car, and the removable floor makes clean up at the end of the day very easy. To be honest, you aren't going to find a better (inflatable) boat in this price range or even for 30 or 40 percent more. Great product, lots of fun to paddle and it comes with a 3 year warranty and 180 day, no questions asked, return policy (if you buy direct from SeaEagle). Hard to go wrong with that.