I have my RSV2 in one hand and my eGo-t in the other. - but I have been happily using my
tanks and mega attys on my RS as well.
I've never relied on a single PV since my first PV. eGo batts are nice to have around mostly because they are generally reliable. Their restricted voltage isn't my favorite feature, but they are reliable and perform the same from right off the charger until dead.
I am thinking about parking my eGo stuff, and I just ordered another extra 18350, so the eGo stuff might end up parked for a long while, but I find some comfort knowing I have the eGo to fall back on.