+1 to most of the above. Wouldn't worry about the toe-clips. I have SPDs on one bike, and they're better, but the toe clips on my commuter work very well. Way, way better than platforms alone.

Sounds like we have a somewhat similar commute, although mine is over the same route both directions and it's hillier on the way out than the way home. Here is what I've found: when I ride my touring bike (a 2009 Jamis Aurora--this is the one with the SPD pedals) to work, it takes me around 55 minutes. When I ride my ancient mountain bike that is my bad-weather commuter (a 1993 Bianchi Ibex with studded snow tires in the winter and an unlockable front suspension--how I bought it and I don't want to go to the trouble of swapping right now), it takes me a little more than 65. I think the bike makes a difference.

Assuming this bike fits you tolerably well, you might want to hang onto it, make it a little more comfortable (the bar ends are a good idea), and save for a decent cross or touring bike. I consider my Jamis either fun-but-practical or practical-but-fun, based on how I have it loaded. Its geometry is fast enough for me to enjoy long recreational rides but it's not a racer. It's on the heavy side and sturdy, but it moves. My mountain bike is a reliable mule for slush, snow and ice, and if I want to, I can take it on some trails and bang it around a bit.

Given that, according to the "how many bikes equations" (n+1 when n=the number of bikes you now have or s+1 when s=the number of bikes it will take for your spouse to leave you), I now can have two bikes, I like both of mine. They're "in-between" bikes. A true roadie might scoff at my Jamis. A true mountain biker would think my Bianchi is relatively useless antique. As a commuter and general lover of being on two wheels with no pretensions to racing or daredevilry (beyond the courageous act of riding in traffic), I love them both.

Happy trails.

PS--If you decide your current frame is too small but are still open to the two bike suggestion, try Craigslist. You could probably sell your current bike and then buy comparable quality MTB that's a little bigger for about the same price. You'd come out even, have a sturdy commuter that fits you a bit better, and still save for that fun-but-practical/practical-but-fun bike to speed your trip to work on all but the bad days. I'll say this: The one way I know to make an $800 steel touring bike feel like a $5000 carbon-framed racer is to ride a 20 year-old $100 used steel mountain bike on studded tires for three weeks and then ride the touring bike on the first dry, above-freezing day. You'll feel like you're in a freakin' time trial!