Considering a Roadcrafter. Seen amazing reviews all over, but does anyone here have any input?

Also, I need everyday storage for my commuting. If I mount a top and side cases, will I see any significant effect on performance due to top weight and drag? I may do an 18t as well if it'll help on the highway.

Lastly, will a well maintained great running gs be operable in temps in the teens and twenties? My last carbed bike died on the freeway in that weather. On the same note,is the electrical system sufficient to wire in heated gear?

I don't have any input on your first two questions, but  #3:

Teens and twenties (I'm assuming fahrenheit) should not be a problem for a good running GS. The slightly lean jetting on US bikes would be even worse at those temps, so going up a size would help.  The stock stator will probably do light duty heating, but full suit, gloves, socks....  I would check the specs, or upgrade to a stator from Electrosport.

Can't answer your questions except for luggage.  I've been using a Shad SH-40 top case for 1 1/2 years and it doesn't affect handling at all.  It will hold my helmet, gloves, jacket and a few other small items.  I sometimes run with Cortech saddlebags as well, and they don't affect handling either.

I have an Aerostich large messenger bag I ride with.  Terrific piece of equipment and the additional stability strap works great.

I use a SealLine Baja dry bag.  Made in America (Seattle, Washington area), and you can strap it anywhere.  I used a mesh stretch net to secure it to the back to the GS.  Cost me about $30, and it's great!  I have the 30 liter size.

http://cascadedesigns.com/sealline/dry-bags/baja-dry-bag/product

EDIT:  As for cold temperatures, your bike will run, but will need a bit to warm up because it's air cooled.  Try using synthetic oil when it's cold outside to help with cranking and warm-up.  The GS's electrical system is a bit anemic.  I'd swap your tail lights and dash lights with LEDs to give more power to other needed accessories such as heated gear.

I have a Roadcrafter and it's great as a "commute suit" that I can wear over work cloths and for touring duty.  I bought a Fieldsheer Roadcrafter knockoff some years back when the Aerostich was in for repairs and it's not nearly the quality of construction nor as quick/easy to get in and out of.  That said, it was about 1/3 the price on some sort of closeout.  The Roadcrafter vents well, so it's good in warm weather as long as you're moving.  In cold weather the collar doesn't seal very well so I use a neck gaiter and a windproof jacket under the suit to cut down on drafts.

I've used my Widder electric gear on the GS, though I've since moved the wiring over to a different bike.  The GS has enough power to run the setup while cruising, but won't keep up at idle, so I have to shut the electrics down in stop and go situations to avoid drawing down the battery.  My understanding is that the GS will support about 100 W worth of additional load at speed.

I've ridden the GS at temperatures in the 20s without issues.  Not really interested in colder weather riding.  The biggest potential issue (aside from hypothermia) is carb icing which tends to happen more at temperatures around or somewhat above freezing and in damp conditions.