I'd rather be swimming...biking...running...and eating cheesecake...
--===--
2008 Cervelo P2C Tri bike
2011 Trek Madone 5.5/Cobb V-Flow Max
2007 Jamis Coda/Terry Liberator
2011 Trek Mamba 29er
How about putting a pair of mustache bars on your 520? I switched out the drops on my Surly for a pair of mustache bars, particularly because of my needs for commuting.
If you are going to buy a separate bike just for commuting, I'd definitely go with a hybrid over a mtb. (I used a Kona Dew for a while, then a Kona Smoke briefly until my son wanted that bike, now a Surly Cross Check.)
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson
I have turned my old cross-country racing MTB into a commuter. It is very light, has only a front end suspension and is very responsive. It's got a fairly aggressive geometry but I like that. Then I put on thinner/slick tires and I was good to go. The reasons why I liked it 1) I never worried about potholes 2) I could jump objects if need be to stay out of traffic or even onto the curb for quick evasive moves 3) it was lighter than most commuters but one should note that it was a $3000 bike new in 1998, so quite high end.
I would recommend looking for a high end used MTB, front end suspension or rigid and making the appropriate modifications.
Having said that, I have never ridden a hybrid so I can't really compare.
I like the idea of using a cross bike as well and switching out the handle bars.
Living life like there's no tomorrow.
http://gorgebikefitter.com/
2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS
Mtb with slicks is a great commuter. Shocks really help in the city. Try craigslist.com for bikes too, lots of older inexpensive bikes.
I let my husband try some thinner (1.3) slick tires I got for my Surly. I don't think I'm getting them back!He rides an older rigid frame mtb to work and said the slick tires make the bike feel like a new ride. bikerHen
Thanks for all the tips/ideas- I'll keep you all updated on what I go with.