Is a visit to Whittier with RV a good use of time?

Best bet if you're towing a TT or FW or in a Class A towing a little guy, is to camp in Portage campground and day trip to Whittier (and Alyeska).

It can be amazingly gorgeous or miserably drizzly.

As several others said, the tunnel portion is almost worth the drive itself. It's one way at a time and flip flops every half hour I believe.

Unfortunately the best glacier viewing is going to be from a boat, so take a day excursion for that as well if you can.