I will very much attest to using what was a mountain/rando style bike initially for a basis of a commuter. Evolving parts spec to tune in relevance has yeilded a very satisfactory result for multi-surface commuting. I use a 20" 1994 Giant Sedona cromoly frame with discs added(custom tab). Hollowtech crank with 48T biopace(yes) double rings. Rear cassette 11-40 9spd. XTR mountain derailleurs and rapidfire rear control. Barcon front control. That was due to the odd trimming tendencies of the biopace rings. The fork is a 2004 Rock shox sid with platform and lockout. The nice thing of the Sid fork is when it is locked it can still 'blow' if you hit a large pothole. Open it up if you get to a construction zone or gravel road/path. Recent enhancement was to add Sun-Ringle Helix 27.5" rims and Clement MSO 42mm tires. The total package and fit is such that it all clicks in and just feels like a resounding yes.
Part of starting with that base chassis is that I have the full XTR level XC 26 x 2.3" wheel mtb that I do races with and it fits like a glove. Drop barring the commuter version was a logical extension of it, particularly since my commute involves a gravel stretch, potholes and other such wilderness liabilites. I commute on either one and the XC version is not bad in itself but the peak speed is definitely improved on the drop bar version. In the steep climb territory its a bit grayer since the XC is 3 ring mtb gearing. Ive had both on 50 mile runs, but 35 is more the typical due to time.
The beauty of the Rock Shox forks like Judy or Sid is they are truly quality pieces for what you get, but nowdays are very affordable. I have gotten a Sid at a swap meet for $80 because it needed a oil change. Long way from 800 new, lol.