I was happy with my 510. I was not happy having to carry 6 batteries and the pcc and making sure that they were all charged constantly.
I got my eGo this past Thursday. The vapor production is heavenly....TH is closer to analogs. I ordered from Good Prophet and got my eGo in 2 days with the priority shipping (well worth the $3!). I also got cartos since I had not tried them but read that they would hold 1 1/2- 2 ml of juice. I ordered a couple of the eGo attys and WOW are they big! I haven't tried them yet. I have been using my 510 attys/carts with my eGo, no problems (unless you count having to refill more often). I usually have to refill the 510 carts every couple hours. The eGo battery lasts me from 7 am to 7 pm most days. I have filled and used 1 cartomizer. LOVE it! It holds enough juice that I wouldn't have to refill all day (if I could stick to one flavor

).
I still use my 510 at night or first thing in the morning. I usually keep about 6 attys/carts all with different flavors going so having the extra parts is great!
KayleePup