Lots of really well stated points, and if I may share my perspective.
In relation to working at a higher sample rate comes down to a few factors: Number one being CPU usage. Number two hard drive space. Don't think about what your working on CURRENTLY, but backing and archiving your projects.
Plan accordingly and go with 96khz.
One thing to note, if your music/mixes don't sound stellar at 44.1 then its a moot point all together.
Also, for me I use a very select few VST instruments I know very well, and if I have a composition that's very taxing in the first place you can forget working at 96khz. Seriously, two or three Diva's and a few NI Massive with 32 voices and that's it for my 8 core 2.66 Mac Pro 1.1. Even with the additional 4 cores as of late its still tough to justify it.
Personally its really really slows down the mixing and creative process, so again focus on getting your mixes stellar sounding at 44.1.
If they already do, I suggest the very very fastest CPU on the market.
For me to work at such a high sample rate, bouncing stems and trying to work with nebula would probably make me feel comfortable with another 4 cores and a few more Ghz processing power.
I took a step back, really really worked on my sonic perspective, sound and musical creativity aspects and am pretty happy.
Projects I'm working on in 44.1 sound a billion times better, with a really cool sonic personality to boot, than the stuff a few years ago started and mixed all at 96khz.
If I could really address those two points listed above I wouldn't think for a second not to work at 96khz on a regular basis.
Also, if your mixes already do sound awesome and you have the CPU and storage, go for it. Yes they will sound way more open, and that absolutely does transfer down via mp3.
192 sounds WORSE, than 44.1 and 96khz every time I've tried.
On the plus side my mid-grade (but rather nice sounding) converters do sound a bit more open operating at a higher sample rate too.
Digital plugins like compressors and eqs sound more musical too. Lets not forget algo based distortion plugins, and yes again a much added benefit to a higher sample rate.