I hiked nearly all of the Superior Trail just this past September; I ended less than 20 miles short of a thruhike because of excruciating heel blisters that were starting to become infected. I don't think the problem was my trail runners
per se so I think you'll be OK with them.
Resupply will definitely be a challenge for you. We sent ourselves maildrops in Grand Marais and Finland. There are also decent grocery stores in both towns.
By definition, you don't face any long 1,000'+ ups and downs like the AT but most of the ascents & descents are very steep. Also much of the Trail is rock and root strewn similar to New England.
Re. water, I used Aqua Mira with no problems. Water availability was an issue in some parts but you should be OK with a May hike.
If you can time it, camp one night at Gooseberry Falls State Park. You pay a reduced rate for backpackers and the backpackers' campsites are right on the lake - much better than the car campers.
I recommend an overnight stay in Grand Marais and dinner at the Angry Trout restaurant. In addition to superb Lake Trout, everything on their menu is health-conscious. For example, all their veggies come from local sources. The only issue is whether they're open in May or not. I know they close for the winter.
Finally if you haven't discovered it yet, the guidebook is geared to day and section hikers, not thruhikers. So the mileage is misstated because it includes side trail miles from parking areas not on the SHT itself.
It's a very nice trail. Good luck. And check out WB's "Other Trails" forums; do a search and you'll find other Superior Trail threads:
http://www.whiteblaze.net/forum/sear...earchid=709988
Oh - to edit your posts, join WB as a Donating Member.