I can't speak to the newest models, as I own a 2012. But I do have a lot of ATV, snowmobile, and motorcycle experience. So I wanted to respond to the "road shimmy" question based on my perspective.
The Spyder's front end handles very similarly to an ATV, but you need a "light touch" on the handlebars like with a snowmobile to get that over-responsive steering thing out of the experience. Due to the upright driver posture, I know that the handle bar riser would help with this. I just haven't taken that mod on yet, because I can be mindful of it. For me, it only becomes an issue where you least want it to be an issue: at high speeds (70 mph and up) like Interstate cruising. This handle bar riser thing depends on your personal ergonomic needs. The taller you are, the more likely you are to want it. I'm 6'1". I feel like my arms about 1" too short (ie. handle bars are 1-2" too low). This causes me to "lean in" to the controls, putting more pressure on them than I should. The issue is that the stability control computer in the Spyder senses the micro-effects of force being exerted on the controls and interprets this as a need for minor adjustments. Sway bars and tire changes and what not can help mitigate this for people who can't or don't want to use activity modifications (OEM mfgs LOVE people like this!). I just have to be mindful of it during rapid acceleration and ease off the handle bars a bit more than feels natural. I admit it is a bit counter-intuitive. Then it isn't a problem.
The rear end of the Spyder, for obvious reasons, handles more like a snow mobile than a quad, but with digital stability controls that are second to none. You may get a bit of fish-tail when accelerating into an immediate right/left turn from a stop; like leaving a parking lot or stop sign and entering into a highway with a relatively high avg speed with oncoming traffic. Mostly, this only happens when roads are wet, on gravel/dirt, etc. On a 2 wheeler, you would go down for sure under conditions the Spyder will immediately recover from without even getting off the throttle. If you're 2-up, this really won't happen much, or hardly at all. But I've done it a few times solo. I live in a very rural area with lots of 2 lane 65-70 mph speed limits with gravel roads and with parking lots adjacent. I instinctively backed off the throttle the first time this happened, and then had to get on it hard after the blink of an eye it took the Spyder to true up the rear end. After that, I tried just staying on it a few times and found that it always trues up in the blink of an eye, even under steady acceleration.
Finally, I'm sure some folks here can point you in the right direction regarding rear passenger arm rest options. They do exist, but aren't cheap from what I've seen. Then again, if you were a GW owner, you are probably quite used to paying a premium for what you want.
On the comms issue, I suspect you'll have to update your equipment. This is a negative reality of this modern digital wireless age. Every few years, stuff becomes incompatible and outdated. You buy a new bike, a new TV, a new computer, a new phone, and nothing works with your existing stuff. My wife and I use high quality blue tooth ear buds with our phones to run in helmet music and nav. If we want comms, we use Jawbone MILSPEC ear pieces with our phones. We have both. We ride separate bikes, but we only use the comms on long trips. The music quality sucks when it is only in 1 ear. The reason I mention this is that our approach is cheaper and totally independent of any system integrated into a specific vehicle (personal portability). So we don't have to buy new gear very often. In fact, our Jawbones date back to 2008 and are still the best in class by a good margin for hands-free voice comms. If you wear a full helmet, this option isn't practical. You have to be able to touch the ear piece to activate certain features. But the Jawbones are AWESOME at cancelling road noise, wind, etc. Just another way of skinning the entertainment, navigation, comms cat if it works for you that runs through your phone instead of the bike, car, truck, boat, etc. FYI, charges last about 8 hours on ear buds and 12 hours on Jawbones.
