Knog lights won't be sufficient for commuting in the dark - check the electronics/gadgets subforum for extensive discussion on lighting options.
For what you describe, the easy "go to" starting point would be a cyclocross (cx) type bike - not a racing cx, but one that allows a rack and fenders to be installed if desired. CX bikes allow wider tires to be used, yet offer a sporty enough geometry for a sporty ride in many conditions.
Fit is the single most important aspect when considering your options, so whatever you do, make sure the bike fits. If you are purchasing new from a local bike shop, they'll help with this. If buying online or through Craigslist/Ebay, you'll need to have an idea of what will work for you.
Now is a great time to be in the market for a new bike - many shops are doing year end closeouts on their 2012 models, so good deals are out there.
I was at a local shop yesterday and saw one of
these on the clearance rack. I was pretty impressed with it, and I think this shop had it on sale for 800 bucks or so. All you'd need to do is put some 32mm slicks on there and a rack/fenders, and you'd be set to go.
Naturally, there are other options out there.
What kind of budget are you looking at?
Do you prefer a flat bar or a drop bar?
What are the "significant" hills like? Since you mention that they all occur within the last mile, this would imply that they are short but possibly very steep. This can influence your choice.
How strong a rider are you? This can also influence your choice. A stronger/fitter rider will not necessarily require the same range of gears for short steeps.
When budgeting, remember that there will likely be some other things that you'll need to allow for, such as lighting, helmet (if you don't already have one), tools/flat repair, rack & fenders (if desired) and bags.
If you're traveling light, a small backpack may do.
You say you work on buses, so you're probably predisposed to doing your own bicycle maintenance. This will save you time and money through the years, and will provide you the capacity to deal with whatever roadside repairs might be called for.