Have fun commuting. 8 miles is not bad. I found that the first few weeks I was going pretty slow and I could realy feel my legs. After about 2 months I noticed that I was averaging much higher speeds without any extra effort. Your body will get stronger.
Since are comfortable on your bike you will have fun. Most of the world does not commute on hybrids, mountain bikes, or road bikes. If you look at Europe or Asia, most bikes used for commuting will be more like what you ride (except they have 1 to 3 gears and you have 21). Enjoy the ride. I've had so much fun commuting on my bike, my co worker talked me into doing a 33 mile ride for the local Cancer Hospital later this month. Next year my goal is to get from my house in a Northern suburb of Buffalo and follow the Erie canal to Pittsford NY (subrub of Rochester) to visit my sister. That will be about 70 miles. This is something I'd never even contemplated before. Getting out there and enjoying the ride has been very rewarding.
Take it easy at first so you don't get burned out. Here are some things I think you realy don't want to be without:
Fenders - It DOES rain in Florida. Even if the rain has passed, you don't want the front wheel straying water and grit up at you and the bike, nor do you want a stripe up your back from the rear tire. You can get these for under $20 for a set of Planet Bike Freddy, or spluge $35 for the SKS.
Rack - I don't like carrying things on my back, especially is it is hot. I want to enjoy the ride. I also carry food, drink, and some basic tools, spare tube and mini pump with me. A nice rack is about $30.
Panier bags - I got a cheap set, the Axiom Appalachian for $29. The bags are nice and hold plenty of stuff. I sprayed them with some extra water proofing stray and did fine during a recent thunderstorm. I've used them for some light grocery shopping we well.
Front and rear lights - I got a set of Pyramid Pro Led light set for $20. I use them in flashing mode during the day to provide maximum possible visibility. So far I've used them for nearly 3 months and the batteries are holding out just fine. I find the extra visability duing the day comforting, but if you are ever caught out in the dark, lights are an absolute necessity. I don't understand how a bike can legally be sold without lights. Ever night I see people out there on bikes. Reflectors help a little, but modern LED lights do wonders for making you visible to motorists.
Breathable shirt to ride in - I love the modern fabrics. If I wear cotton, I am soaked when I get to my destination on a hot day. With the "coolmax" style shirts I stay much cooler and don't get all wet. I am also a cheap skate so I don't buy anything unless it is on sale. I have not paid more than $19 for a nice riding shirt. I also like bright colors, yellow or that "nasty" hi-viz yellow/green. I want to be seen on the road!
Rain coat or poncho - You are in Florida sooner or later you'll be caught in one of those afternoon monsoon rainstorms. I have an old Agu Sport rain gear set that I bought in the Netherlands back in the 1980's, but it is dark blue. It still fits and works fine, but don't like that I can't be seen well. This week Nashbar had a one day sale and got a H-Viz rain coat for $12, and no cost shipping. You don't have to spend a fortune to properly equiped.
I ride in my work pants when it is cool. If it is hot I ride in normal shorts. I only use bike shorts if I know I'll be riding more than 16 miles at a time.
For shoes, I bought a set of breathable athletic shoes. I needed casual summer shoes anyways and came accross a set of Merrell Moab Ventilators. These shoes vent much better than normal sneakers, and do an excellent good job of keeping my feet from getting steamy.
Enjoy the ride,
André