I like Ubercart for the most part, but as I've mentioned I think I've reached the limit of what I'm willing to do with it. I think it needs a full re-write, which is why I'm happy Drupal Commerce is going on. It should take a lot of the things learned from the short sights in Ubercart and hopefully rectify them.
I'm also happy Ubercart is available for Drupal 7. I'm very happy it's a straight port of the D6/UC2 version with out improvements. One of the problems the Ubercart 2.x for D6 was that it took too long to create after D6 was out. This slowed adoption. This wasn't a specific Ubercart issue, but more of a Drupal community issue. The Drupal dev's have done a good job of recognizing issue by creating the #D7CX pledges, which ask for a straight port of the D6 version, instead of doing improvements during the D7 migration. Wonderful decision in my opinion.
Having Ubercart around in the D7 space will allow for two things:
1. It will allow those with existing D6/UC2 sites an upgrade path to D7 should they choose. Those users will know what they're getting with Ubercart as it should mostly be the same as the D6 version. In my opinion development and feature improvements should stop in Ubercart and an effort should be made in porting good contrib modules over and bug fixes. Site maintainers can take over the improvements from there.
2. Since there's an upgrade path for existing users, development Drupal Commerce can de-couple from Ubercart and something new (and hopefully better) can be created. I'm personally interested in using something new, but may port some old sites to D7/UC if there's benefit in that. Since Drupal Commerce is a new project there's no need to create an upgrade path for it. An upgrade path from Ubercart to Drupal commerce can be created by those who eventually will need it (people like myself).
This is just what I'd like to see. If Drupal Commerce is complete sh!t, then obviously I'd go back with Ubercart...but I doubt this would be the case.
Note: I'm not a Ubercart developer, just someone who makes sites with it. I don't actually know the direction people are planning, so I can't really talk to what people will do. These are just my assumptions from what I've been reading/following.