I don't have a problem with IE so long as MS takes a more active role in supporting standards, which they are supposedly doing with IE7. Now, if they wait another 5 years to update the engine, then...
I don't really care if they use proprietary technologies, either. Just so long as they support open standards as well. That should be priority #1.
Ideally, it'd be nice to see a single rendering engine across multiple browsers, but that's not likely anytime soon.