There is a lot of literature saying that subclavians have lower infection rates, and there's other studies showing IJs have lower pneumothorax rates, and there's an equal amount of literature saying that there's no significant difference. What does that mean to me? Literature exists out there to support whatever bias we have, causing some people to do all IJs and others all subclavian, based on our comfort level.
As for ultrasound for IJs, it is the standard of care, and the ACS has issued a position statement to that effect. When it is available, and you don't use it, you will have a hard time defending your decision if a complication arises. Unfortunately, I have done lots of lines without sono, based on attending preference, so I'm comfortable with this, but I will never do this in practice.
As a first line, I usually place subclavians, mostly because I feel it is an easier line to take care of (nothing more common than seeing an anesthesia-placed IJ flopping around in the wind without a sterile dressing POD #1). Also, it seems that my junior residents have less experience with subclavians, so I walk them through it for that reason (on trauma, they'll have to place mostly subclavians due to the c-collar, and need the skillset). I buy into the lower infection rate, so that's my bias.
Dialysis catheters and CVLs in renal failure patients all go in the IJ with me. Portacaths, being tunneled, have no infection advantage in the subclavian, so I go sono-guided IJ for that as well, as I feel there's a smaller chance of pneumothorax with IJ (more bias, and I'm familiar with the literature).
Now, the future probably holds sono-guided subclavians, so I'm interested in developing this skill.
Finally, for arterial lines, I admit that I do most of them without ultrasound. If I miss, and sono is available, I usually use that on the same wrist prior to changing positions. If the patient has no pulse, but still has good ulnar perfusion, I will use ultrasound primarily. I am a big advocate of sono-guided a-lines, and I believe it's a skillset we should all develop. I very rarely am unsuccessful in placement, very rarely go to the groin, and very rarely spend more than 15 minutes in there trying to place it, because of my acceptance of ultrasound guidance.