Wave is for solving the key problems with email in a corporate environment:
1) It's hard to track (will presumably offer an API or be trackable by widgets)
2) It's hard to use it to collaborate on a piece of text to be sent out to someone else or included in a document (which is what it's used for half the time...)
3) When adding new people, it's hard to ensure that they have a clear view of the beginning of the conversation - often they get a garbled, over-indented mess in reverse chronological order, that's hard to follow.
4) When adding new people, often they get dropped again if someone replies to all from the wrong email.
5) It's hard to keep multiple conversation branches going. If you're collaborating with 5 people (hardly extraordinary) on a 2-page document, and they each have 1 distinct comment, and each of these comments requires a brief exchange (back and forth 3 times, let's say) before it's sorted out, you'll end up with a fairly messy conversation once it's all flattened out.
6) It's hard to attach files (particularly large or numerous files). And when you add extra people to the conversation, they don't see those files anymore. If there were multiple files sent at different time, sending all of them to the new participant is a pain in the ass.
7) When discussing, say, a document, correcting even a small typo requires a full email instead of being able to just dive in and correct the typo.
There are no doubt more, but this is what I can come up with fresh out of bed.
Wave is for solving the key problems with email in a corporate environment:
1) It's hard to track (will presumably offer an API or be trackable by widgets)
2) It's hard to use it to collaborate on a piece of text to be sent out to someone else or included in a document (which is what it's used for half the time...)
3) When adding new people, it's hard to ensure that they have a clear view of the beginning of the conversation - often they get a garbled, over-indented mess in reverse chronological order, that's hard to follow.
4) When adding new people, often they get dropped again if someone replies to all from the wrong email.
5) It's hard to keep multiple conversation branches going. If you're collaborating with 5 people (hardly extraordinary) on a 2-page document, and they each have 1 distinct comment, and each of these comments requires a brief exchange (back and forth 3 times, let's say) before it's sorted out, you'll end up with a fairly messy conversation once it's all flattened out.
6) It's hard to attach files (particularly large or numerous files). And when you add extra people to the conversation, they don't see those files anymore. If there were multiple files sent at different time, sending all of them to the new participant is a pain in the ass.
7) When discussing, say, a document, correcting even a small typo requires a full email instead of being able to just dive in and correct the typo.
There are no doubt more, but this is what I can come up with fresh out of bed.