An alliance, yes. That would be good. As for an all out merger, probably not.
The fact is, Sun is as much an innovator as Apple is - though in different directions. If Sun's visions were achieved, we'd all be hot-desking at work on systems that cost only $200 and perform better than a current $4000 system. We'd have seamless networking and communication using free, open standards. We'd have no real hassles hooking our TV sets and washing machines to our home computer networks.
The ideas that come out of Sun are fantastic, and they do have a lot in common with Apple: they give developer tools (ie Java) away for free, they support Unix, they create quality hardware and servers, and they always use open standards whenever possible. Although their approach is vastly different, an alliance would be a pretty good thing. However an all-out merger might stifle the creative power of both companies.
An interesting thought, though.