YES! It absolutely is!

I just got back from a five day trip up there with a friend of mine. We did a four hour cruise around Prince William Sound out of Whittier--I'm not sure what the longer tour would get you, but on our tour, we saw otters, a whale, birds and a glacier. Bring a heavy jacket (maybe a rain jacket), even in June.

Your Seward trip sounds exactly like ours: we stopped at the Alaska Wildlife Conservation Center just outside Whittier on the way down, then we went to the Alaska Sea Life Center. Exit glacier was very neat to see even if it was raining when we were there. If you go to Talkeetna, and the weather is nice, do an aerial tour of Mt. McKinley. If you can get over the fact that you're in a 8 seat plane, it's spectacular. The views you get on the flight to/from FAI are nice, but this is much better and takes about 90 minutes. Just one word of caution: the drive from Homer to Talkeetna will take about at least eight hours, probably more. That might be a tough one to do all in one day. The drive from ANC to Talkeetna is very pretty if the sun is out. I'd suggest trying to show up last minute for an airplane tour. My friend and I saved about $150 each on our tour by doing that.

Next time I'm up there, I'm going to throw in a side trip to Nome/Kotzebue. I don't think you could do more than a day in either place, but I think it'd be worth checking out.

Our itinerary was more "touristy" since neither myself nor my friend had been up there before. Here's more or less what we did:

Day 1: ANC
Day 2: ANC/Talkeetna (Mt McKinley aerial tour)
Day 3: Seward (AWCC, Sea life center)
Day 4: Exit Glacier/Whittier Glacier Tour/ANC
Day 5: FAI (flew to FAI)
Day 6: Fly home

Depending on where you're flying, the "red eye" flight from ANC isn't that palatable. It's only about 3 hours down to SEA so you can't really get much good sleep on the plane.

If you're interested, I have a ton of photos I took from the glacier tour and aerial tour.