Update on my pen situation:
I bought two pens since I started to stack AOD and Serm. I am using Tirz with syringe only and I find that the pens are nice, fast, and easy to use with less pain than the syringe. The only negative is filling the cartridge and eliminating the air. I seem to lose probably a good 5-8 units trying to get the most stubborn air bubbles out. Its a 50% success rate when I lose less than 5 units (estimations, of course)
I agree that only with a daily dosing is a pen helpful, otherwise there isn't much of a benefit unless you are squeamish about needles.