I got the butane solderer, after returning back the ColdHeat that didn't do crap for me.  In my opinion Butane is the best way to go : It's portable, light , easy to handle, adjustable heat and less messy.I'm also surprised at the refill need for the unit , it lasts surprisingly long.          

     About the cancer warning...all soldering tools will have it, as you are working with chemicals+heat.     It's same butane gas that fills up your lighter and no one ever had a problem with that.

So for me - I preffer the butane unit, for the ease of use and the performance.

* Funny thing : the label says that the thing is harmful for the people of  CA , i live in NY - so i guess it wouldn't affect me. ......right.

All this talk about soldering and no pictures!!!!

When soldering you need to make sure the final result is nice and shiney, all the way through. Apply heat to both wires and apply the solder to the WIRE, NOT the iron.

Also, when possible, make sure you have a solid mechanical connection before trying to solder.  This basically means wrap one wire around the other wire tightly so that it is snug before its even soldered.  This is practical in 90% of car soldering, but when it comes to some tach wires you have to settle for whatever you can manage.

Another important thing to try and do is keep all the strands of the wire together.  If the strands get spread out when you solder them they will leave single strands standing straight up.  This isn't that big of a deal, but it hurts like heck when you stab yourself with a single copper strand (especially if its hot still).  Also, these single strands will poke through the electrical tape and could potentially short out.

The above joint was made by me (I don't generally take pictures of other peoples soldering...) and was made by a butane iron I picked up at www.PartsExpress.com.  In my old age I've gotten away  from my Craftsman soldering gun that I cherished as a professional installer because, simply enough, the butane is quicker, easier, and doesn't have to be plugged in.  I don't solder enough to go through a lot of butane, so it works out.

Oh, another important thing is to use the correct heat for the project at hand.  I have a buddy who tried to solder a mod chip on his Playstation using a 30 watt iron (~950 degrees or so).  For most wire (16 ga and smaller) I try to stay around 650 degrees, IF you can control the temp.  My 'nice' iron is a Pace ST45N that features digitally controlled temperature.  You select the temp you want and it maintains it, pretty cool for a soldering iron!

Once you get the hang of soldering you'll quickly see the benefits and will never want to go back to butt connectors.

Remember, when you're done with the joint that shiney solder is good, dull solder is bad!