Finally bit the bullet and purchased my first upcut spiral bit. Using it to cut mortises (or dados) is a pleasure compared with a straight bit. Plunging effort isn't any easier, but once you've got the board down on the bit (on a router table), moving the board (in my first attempt, red oak) over the bit is FAR easier and the results are superb. I looked on line for bit prices and was dismayed to see that most hover just under $50 for a 1 1/4" deep, 1/2 shanked 3/8 spiral upcut. I ended up getting a Freud locally for $39. Tax was less than shipping would have been on line. Another benefit is there's no sawdust packed in the mortise as when using a straight bit.
Sidenote: I Googled to see if the proper term is "upcut spiral" or "spiral upcut". Seems there is plenty of references to either term!
dave