Well, today was my first commute! It was just under 9 miles to work this morning and I averaged about 12 MPH (fairly flat rolling hills, no major climbs). I definitely went out of the gate too fast and got pretty tired at mile 5... there was a lot of slow pedaling and coasting :-) (never got off the bike though). The butt is feeling fine so far with the Brooks saddle... we'll see how it feels this evening and tomorrow morning. The weather was perfect (68 degrees, no wind, clear skies)
I ended up getting a Giro Xen helmet (bit the bullet and got the helmet that fit even though it was pricier then I wanted to spend). I also managed to borrow an Arkel Commuter pannier which is pretty nice if you need to haul a laptop around. I'm sticking with simple platform pedals for now until I get more used to the bike / biking (shifting, riding smoothly, signaling turns, etc.).
Thanks for everyone's help so far!