Yeah..I'm using an eGo and I freaking love it..
Yes you can use your current 510 atties and carts on it..even a 510 battery to 901 adapter to use cartomizers on it (though with the atty cone in place it really stiffens the draw)
it's very slightly longer than the 510 and about as big around as a AA battery...so to me in the hand it feels like a stubby cigar...I actually hold it to use the button with the side of my thumb, and wrap my index finger over the top of it like I'm holding a pencil...feels very comfortable and natural there..
The atty cone...besides just making it look streamlined changes the draw somewhat in that it stiffens the draw slightly, and traps the warm air so the air moving through is prewarmed..seems to improve flavor and vapor production slightly...as a bonus for me it also helps protect the connection point between battery and atty..I'm in a very physically demanding job and I've snapped a 510 at the connection before..cant do that here..
Battery life wise...in the kit you get the two..and I just ordered a spare atty cover so I had 2 complete units..and I rotate between 2 different flavors..and between the 2 I'm lasting all day...actually I'm recharging at night before bed before they're even done..it seems out of the box i topped em off and they lasted like 7 hours and after a full recharge like 10+ hours (in contrast a standard 510 was lasting me 1-2 hours)..
As for the charger situation, The charger from janty is a "fast" usb charger that puts out 420mA with a wall wart adapter that can do 500mA so it charges from dead in 2.5 hours..the TW version comes with a standard 510 mains charger and an adapter so it takes something like 6 hours...I have one of these
JOYE510 USB Charger and just tried it on an eGo battery and it works just fine..so I guess it depends on your universal charger and how much shell there is on the charger before the connection really..I know thats why it won't fit the standard 510 charger and TW had to have a charging adapter (the post is too far inside the housing on a standard mains)..
So yeah for staying at standard 510 voltage in a sleek slim compact and comfortable design I think it's pretty much perfect..
For dripping a little less so..because the atty cover makes it pretty impossible to tailpipe..so you need to use the blank cart or add something like a T tip..but if you're using carts yeah getting closer to perfect...the addition of the tesla filter when janty gets that perfect even more so..
By the way this was my first ever janty purchase so I'm not just being a janty fanboy either..