I actually started vaping in early june, but had to send that pv back (POS) and smoked for another week before I got my 510, so for the purpose of this, I'm saying I started when I got my 510 on July 6th.
Ugh! Acne!!!! I've been one of those lucky people who's never had issues with acne. I've probably had fewer than 100 zits in my whole life (I'm 26).
NOW, nearly 3 weeks into vaping I have zits! And they started poppin up about a week ago. Every day I wake up thinking, Why?? It's not that time of month, and even if it was, this is excessive. Am I eating different? No. Hmm... Maybe the summer heat... that's never happened before though. Low and behold, there's a correlation! I can live with a few zits, but know not knowing why they appeared is annoying, lol.
I quit smoking for about a year before when I was 19 and I don't remember this happening... but at that time I'd smoked solidly for about 5 years, and now it's been a total of 12 with that one year break (and I started when I was about 12, but didn't really smoke on a regular basis till I was 14, so I don't count those 2 years), so maybe that's what made the difference.
Glad to hear that one goes away! Okay, lets see, what else....
Acne (yes I know, repetive)
Sore muscles!!! I had no idea that this was related! Now it makes so much sense!!!
Bit of a sore throat and slightly swollen lymph nodes
A couple little mouth ulcers (I get these from too much sugar too...)
At one point it felt like my salivary gland was clogged. Actually that's happened a couple times. Very very uncomfortable. It only cleared up when I cut back my vaping.
Throat clearing from smoking went away for a bit, then came back from vaping

That's pretty much gone now
I think that's pretty much it. Nothing major really. I feel much better than I did smoking. I've also done the whole nic OD thing, overestimated and ordered 26mg nic juice when I started, lol. Now I usually use 12mg, 18mg, or 0mg depending
But yep, that's my experience so far.
During the first few days I experienced nicotine withdrawal. I get it quite bad anyway, headaches, nausea, shakiness and usually end up sleeping a lot. Doesn't last more than a few days and could be attributed to learning good techniques for getting the best out of the eCig.
Had a cough that didn't go away for 3 weeks(ish).
Also had an acne breakout - started about two weeks in and is just about clearing up now, we're at 5 weeks today (woohoo!)
I still have very very slight cough, I expect that inhalng anything which isn't clean air acts as an irritant. Hope that logic is correct!