Hey typocinnamongirl!
As others said, the Riva battery life alone is probably worth the upgrade, and you do need a new charger. The vaping experience... is pretty similar. I find the cone changes the draw and heat in a way I like - others don't. But it's a subtle difference. I think that because a higher mAh battery like the Riva/eGo keeps performing at max voltage for longer, it gives the illusion of more power. It's not. It's just that the 510 battery life is so short that the power drop that happens as the battery runs down takes up more of its total battery life.
As to LR's... I'd be careful. I am one of those people who has had problems with it. I overheated the switch on a 900mAh eGo battery with an LR and destroyed the it. The battery was only a couple weeks old.
I do vape heavily - maybe it's not as big a problem if you don't. But all the same, Riva/eGo batteries aren't designed to deal with that kind of power. The amperage is too low, and the switch isn't robust enough.
Lots of people do it with no problems. And maybe if you're careful you won't have issues. But the risk is definitely there.
The only thing that is really designed to handle an LR is a mod, using a 2.5+ amp battery, and with a high-grade or mechanical switch (which is what I use now, with no problems).
LR's seem to improve some flavors, and hurt others. The atomizer gets hotter and vaporizes faster, so it does change the way a lot of juices taste. You'll have to play with it to find what you do or don't like.