Why Talkeetnas?: I often contrast this route with the classic Nabesna to McCarthy Wrangells route. While the Talkeetnas lack the sheer scale and dramatic alpine scenery of the Wrangells, this route is more river-centric with better whitewater and excellent fishing. That is not to say the Talkeetna route lacks alpine appeal. The Terrace Lakes offer excellent scrambling and scenery, and both hiking sections of the route offer imposing views of Denali on a clear day. Both times I have done this route we saw thousands of Caribou migrating along the Susitna. Bears are abundant as are grayling, trout, and salmon.
Why Packraft?: This route maximizes paddling and minimizes transitions. Along the way, there are many tributaries to the Susitna and Talkeetna that are worthy paddles in and of themselves. It is a true wilderness experience, and it is unlikely you will see anyone on this route until the last few days on Clear Creek. Hiking at low elevations in the Talkeetnas can be painful, and this route avoids much of that by primarily traveling on rivers or in the alpine (there are still 3 notable days with bushwhacking!).
Difficulty: Generally a class II-III route with opportunities for additional whitewater in the tributaries, such as the Oshetna, Kosina, or Yellowjacket. The Maclaren and Susitna rarely exceed II+ with the exception of Watana Canyon. The canyon provides a short III-IV- experience, but can also be easily portaged on the game trail to the south of the canyon. Clear Creek is the paddling highlight and offers more consistent class III fun and nice canyon scenery. The hiking is generally open, carpeted, alpine terrain. Expect to do some serious bushwhacking any time you ascend from or descend to the river.
If you are moving daily, two weeks would be a sufficient length for this trip. If you are paddling any of the tributaries, fishing, or doing any peak-bagging, I would budget more time. If you wanted to re-ration by plane along this route, the logical options are at Watana Lake (w/ Ray Atkins) and Yellow Jacket strip (w/ Mike Meekin). The crux of the logistics is figuring out your vehicle shuttle. The drive from the take-out in Talkeetna to the put-in at the Denali Highway bridge over the Maclaren is 4.5 hours one-way.