I got the 'vert back this afternoon. Turns out a cable needed to be adjusted. It's now working fine, forward and backward. I took it for a little shake-down run, about 35 miles or so, the lag I felt in first gear was present at first but it went away and didn't return after the transmission got warmed up. I guess things just needed to settle in a bit.
UPDATE–Well, it seems it's still not cured. I went to back the car out of the driveway earlier today to take it for a state inspection so I could renew the registration and I still can't always find reverse first try. Whereas the previous transmission had slop between Drive and Third, this one has it between Reverse and Neutral. I have to jiggle it back and forth a time or two to get it into reverse and I don't really feel it in the shifter, just when I take my foot off the brake and it starts moving backward. Of course, an incline can make that deceiving. Oh well, guess it's back to the shop once again.