Basically I am posting this from my perspective as a "lay" e-smoker. Of course this is my opinion not as a product tester, just as subjective individual who has converted e-cigs.
Like most cigarette smokers, I have been longing for years of kicking butts and have tried pretty much everything I can to quit. (not so much for the nicotine, just the other nastinesses associated with traditional smoking) I had heard of the e-cigarette technology years ago when it was introduced in China however amazingly enough, the gadget head that I am, I never looked into it until recently. Reason: the very false idea of vaping being prohibitively expensive. I am glad I researched it and proved myself wrong.
Another gadgety friend of mine spurred on conversation about how he wanted to find an alternative to smoking and of course that made me do into countless hours of research and eventually trying one out for myself. All I can say is WOW, what an experience! I'm a fairly recent convert to alternative smoking, and I can see myself never looking back.
Being a noob, I was quite ecstatic to find Jason of ElectroNicStix, who happened to be local reseller. He is a wealth of information and is very pleasurable to work with. He took the time to educate about various e-cigarettes without the feeling of obligation to buy from him. In fact, he gave some very helpful hints for my first e-cig which was purchased through another source, and was quite responsive/helpful in assisting me get a replacement e-cig while my original one was being RMA'd.
Initial reactions on e-cigs I've owned:
My first e-cig was a ultra mini style by Smokestik which I chose because it "looked the part" of a real cigarette. I figured it would be an easier transition off of analogs to vaping. I honestly can't complain much about it except in comparison to ones I've owned since then. Initially I was stoked to have an ecig, until after a week the atomizer failed.

It happens, electronic devices fail, and I can't really knock anyone or a company over that. I did find it somewhat difficult to track down the company for a return (it had a 1 year warranty) and the response turn around time was slow. It took 3 weeks from the time I got instruction on how to return the item/ship it out until I actually received the new unit.
Jason at electronicstix.com had a DSE901 in stock for a very reasonable deal (Significantly less expensive than my Smokestik) and I figured I'd give it a try.
Night and day difference! The form factor of the 901, although longer was SO much nicer. Fits comfortably in my mouth...I've smoked tipped cigars/cigarettes before and never liked the feeling so I was sceptical. But it was amazing how balanced it was. The draw, even with two holes was so much more smooth than the Smokestik...The vapor production, battery life, cartridge life, everything was just orders of magnitude better than my original one. And, mind you at the time I was ecstatic of the Smokestik until it failed! The best part about it (this sounds weird) but, it doesn't look like a cigarette. It's elegant, almost that 20's hollywood actress feeling. (I'm not saying it's feminine, it's just, well... sexy in comparison to the ultra mini) Oh and I failed to say that the throat hit was just amazing, very close to that of an analog without being overpowering.
I have been vaping my 901 for almost a month now, and on the original hardware. I am just amazed.
Jason had told me he was expanding his line to include the Yeti (JOYE501). After doing some research, and being a big gadget lover... I, of course, had to have one.
WOW! Just amazing! I was blown over by the 901, I have zero complaints about it, and I would not hesitate to suggest it to a noob or even a seasoned e-cig smoker... But the JOYE501, blows that out of the water! The four hole atomizer allows for an even smoother draw, the carts last even longer than the 901, and the batt life awesome!!! I couldn't even fathom that it would be better than the 901 but the 501, yeah... its luxurious to say the least. This thing practically smokes itself, and the vapor production, I would say is more dense than a cigarette. As far as form factor, sorry the DSE901 is still sexier. I love the flat tip and the weight of it. But form over function... I guess that's a personal decision. They are both valid in different circumstances.
So for me... Out and about to "blend in" (aka party cig) my smokestik. Not the greatest vapor but it looks the part.
Amongst friends, just to chillax and be comfortable... the DSE901.
And for "my time", when I want a great throat hit, lots of vapor...aka home use... the Yeti JOYE501.