Run my own business so have used them all at some point. Because of this, I also know most of the drivers which does help.
Fastway - wont deal with, dont even like when they have to deliver stuff to me!! (Some stuff has gone awol).
DHL - good to receive things from. Have never sent anything with them.
FedEx - probably the most expensive to deal with, sending anyway, and generally straight as an arrow so if there's charges to be collected, they are collected! Can be slow as Christmas for international deliveries no matter what you pay for. Recently had a tiny package from South America supposed to be here in a week or so, ended up staying in Columbia for nearly 2 months for some reason even customer services couldn't explain! It did arrive though eventually but really Chuck Noland could have delivered it quicker!! On the flip side, if it's coming from USA, that package will probably be here quicker than An Post local post!!
An Post - good, quick, sometimes crazy expensive for packages. Online paying DIY for packages is great though. If it's international it tends to be crazy expensive. I'm 40 minutes from the north border, so if a package has to go to the UK, I tend to just drive to the nearest Royal Mail PO as its cheaper & worth it.
UPS - OK...problem is they're still really Nightline...just wearing the brown style American uniform!
DPD - Great. I use them to deliver and have deliveries from them weekly. Nothing goes missing, they give you an hour delivery window, and it's generally always the same delivery guy...and yes, this makes a difference.