Spazmogen, you sound like my doppleganger when it comes to giving blood!
My experiences mirror yours almost exactly. As I mentioned, I've given blood a number of times. And I've also had my fair share of blood drawn for diagnostic tests. Most of these experiences have been tolerable, although not completely free of problems.
Apparently my viens are small and hard to puncture. The technicians almost always have to try multiple times before they succeed. On more than one occassion they have had to give up after multiple attempts on each arm and go fetch a more experienced, more skilled phlebotomist to finish the job.
Despite this, I usually didn't experience much distress, and once they succeeded I would happily watch in fascination as the blood flowed through the tube to be collected. Blood itself does not make me squeamish or queasy.
However, things were a bit worse the last few times I gave blood or had it drawn for a test. In particular, one time the plebotomist was just completely inept. Four times she tried my right arm, each time stabbing, missing, pushing in and out, jiggling back and forth, and literally digging around with the needle inside my arm beneath my skin. The digging is the worst part.
I withstood this with sufficient stoicism for a while, but eventually it got to be too much. After she switched to my left arm and failed two more times I started feeling strange. By the third failure on my left arm I was starting to get clammy, the blood was rushing in my ears, and I was starting to feel light-headed. I told her things weren't going well and that she really needed to get it right on her next try. As she dug around on her fourth try on the left arm (eighth try total) I really started to feel sick to my stomach, my head was getting really light, and I broke out in a cold sweat.
At this point I told her "Enough. You are done." She stopped and I had to sit for a while with my head down, put some towels soaked in ice water on my forehead, and sip some cold water. After 45 minutes or so I finally recovered enough to drive myself home.
I had to go to another clinic to get the job finished, and never went back to the first clinic.
That was the experience that really soured me on giving blood. It wasn't the only bad experience I had when giving, but it was definitely the worst. Yes, I survived it and could do so again, but it isn't an experience I wish to repeat.