I like the 510. It's not "be all and end all" by itself, but it is the basis for a lot variations that have come since it's inception. And 510 atomizer is the gold standard which others are compared.
OK, that being said, if you're not sure about e-cigs just yet, and if you want to start with one, it's a great choice because if you do like it, you can upgrade in the future.
The first upgrade you might want after you decide that the 510 is a good rig is a PCC. It basically looks like a metal cigarette pack that can hold and charge an extra battery plus a couple of extra cartridges. It can usually recharge your batteries 3 to 4 times before needing to be recharged itself.
(I use them when I don't want to pack a "man-purse" full of supplies around with me, and I know I won't be gone from home more than 3-4 hours.
The next upgrade you might want to try is either an eGo or Riva 510 system. They can still use the 510 atomizers and carts, but have a larger battery about the girth of a mini-mag flashlight. They can give you anywhere between 5 to 10 hours of vaping between charges. At this point, they don't really look or feel like a regular cigarette, but they do the job very well. (You can get a PCC for them too, but now you're looking at something about the size of small diary or personal planner.)
And every day, something new is being added to the arsenal like Mega cartridges, Tank systems, and who knows what tomorrow...
I tend to use them all for various times and places.
But if this is your first, you can't really go wrong with an original Joye 510. It's a cheap, reliable entry into vaping, and as I said before, if you like it - great. If not, you aren't out a lot of money.
Oh, and as to your original question about round or "fluted tips?
I buy a lot of my equipment from CigNot.com. A basic 510 set of 2 batteries, 2 atomizers, charger and 5 carts runs for 35.00 even. You can choose whether you want flat or round carts simply by asking for them in the comments section during checkout. (And no, I don't work for CigNot, I'm just a very satisfied customer.)
I hope that helped, and didn't muddy the waters.
And good luck!