My view of Sun and their history
From its founding in the the 1980s through the early 1990s, Sun was a powerhouse that delivered both a stream of technical innovations and an evolving range of machines, from small workstations through large servers, that were excellent values. While never quite as sexy as SGI (even if they sometimes tried hard), Sun's workstations were something that you could dream of having on your desk even if you weren't a Hollywood SFX worker, a CAD/CAM operator, or someone with supercomputer results to visualize. And their servers were the sensible default choice for basically everything, from small to large.
The wheels came off the wagon in the mid 1990s, starting when the features of Intel PCs began making everyone's low-end workstations look dowdy. Sun did not really react in any effective way to the relentless march of increasingly featureful PCs and Intel's increasingly capable CPUs. While Sun made abortive, half-hearted, and overpriced attempts to have some x86 products, it was very clear that their heart wasn't in it.
(Even when SPARC held the performance edge, for basic workstations it rankled that everything else was worse than on a PClone; you got worse graphics, worse serial speeds, proprietary keyboards, and so on.)
By the late 90s Sun and the SPARC architecture was no longer competitive with x86 hardware; Sun machines were invariably overpriced and had less features than comparable PClones, where there was anything comparable. From my perspective as a potential customer, Sun's reaction was to trade on their past reputation (essentially demanding a significant premium for the Sun name on a machine) and their very large servers, where they still had no x86 competition.
(In 1999 we evaluated new workstations for an undergrad lab that had previously been using X terminals and low-end SGI machines. There was nothing from Sun that was even vaguely competitive with PCs; that the Ultra series was then using PC components just made the cost, feature, and performance differences more pathetic and embarrassing.)
In a demonstration of the advantages of good marketing and sales, this strategy worked well enough to keep Sun in business. However, it did not endear them to me; from my perspective, the old Sun (the one that delivered value) had mutated into a marketing driven organization that was playing people for suckers. On the technical side, Sun seemed to be stagnating or at least ineffectual, unable to deliver anything particularly impressive that would justify Solaris over one of the free alternatives; Solaris was left to be trumpeted as merely 'more reliable'.
Starting sometime in the early 00s, Sun (the old Sun) woke up. It started making competitively priced and quite attractive generic x86 hardware, it made a real commitment to x86 in general, and it eventually did something novel with SPARC. It continues to be mired in old habits, but there's some excuse for that. In short, it is once again an exciting company, although one with some old baggage (just like every company).
I don't think that Sun is unusual for following this trajectory (except the last bit); all of the old Unix vendors followed very similar paths. Sun is just unusual in surviving, which I think is at least partly due to how strong it was up through the early 90s (and I suspect that Java didn't hurt). Similarly, I don't think that Sun has made more than the usual number of moves that are inexplicable or mistakes. Even the nadir of their late 90s period was commercially successful, just irritating.
(And it is not as if riding your brand into the ground is uncommon; my impression is that there are all sorts of reasons for the sort of organization paralysis and denial that causes that. The novelty is companies that manage to pull themselves out of the situation.)