First, the car stuff:
My wife drives a stick almost every day, my sister used to, my Mom can, my Grandma can.
I learned to drive on a 1959 Austin Healey Bugeye Sprite in 1987. We still have a '63 Big Healey (BJ8) cottage car in Michigan. My truck is a stick too.

I find the Mtn Bike the MOST flexible platform:

I commute 25 round trip miles on a mt. bike with 20 year old knobbies. It wasn't $500. It was $50. 1987(ish) Jamis Diablo. Rigid bike. Got it at the Pawn shop. Easy to mount up a flea market $2 rear blackburn rack, and let's face it, bars are bars when it comes to mounting lights.
1 bolt to pop on a set of semi-effective fenders. (I have to lift up my feet for deep puddles.) So was it tough to make it a "commuter?" no.

What is my commute like? Well, with the mt. bike I can vary the route. Single track dirt, MUP, and a little road. If I had a hybrid or a road bike commuter, I don't think the singletrack would be as "fun." Bashing up a curb, running over snakes on the single track, rollin' through the mud where the trail is under construction = give me the mt. bike!

Weight of chaingaurds and stuff: Who cares! It is a steel framed bike with a rack and panniers for crying out loud. My lunch weighs way more than a chain gaurd! Downshift and wait a little longer to get to work, or pedal harder.

Maintenance: Well, so far, I've oiled the chain and greased the headset. I'm confident that is all the maintenance this bike has seen in 20 years besides a new back tire. Shifts fine. Shoot it is even indexed shifting (thumb shifters).

Tires: I know it would be easier on my slicks, but they SUCK SUCK SUCK on anything but pavement. They even suck on wet grass. I bet a better tire would make a 1 MPH difference with the same amount of effort. I'll stick with the dry rotted gumwalls. I'm savin' the planet runnin' my once rubber tires into dust.

Brakes: Rim brakes are not the best in the rain. Fine. I know that. I pull the lever a little harder. The ol' cantilever front and U-brake have nver left me thinking, "gee, I wish I had better brakes on this thing."

In summary for the original post: Ride a bunch of bikes. Borrow from neighbors, bike shops, shoot, you can come ride mine for a week. I don't care. Find out what works on your trails, paths, and streets. Find out what feels best to YOU. Find out if a mountain bike is "fast" enough for you. Strongly consider a used bike for a commuter. The price difference per unit of quality bike is amazing. (A $100 used 15 y.o. bike will get you 90% of the bike that $500 will get you new.)