Purple prose is what happens when a writer overwrites. Characterised by a use of unneccessary or surplus words, using too many adjectives and descriptors and generally waxing poetic when there's just no need. It's apparently frowned upon, viewed with disdain, about as popular as a lerposy-stricken masseuse.
But I've got to be honest: I love it. I'm a fan of Edgar Allen Poe and HP Lovecraft, writers who knew their craft and revelled above all else in the use of imagery to convey atmosphere. Was their prose purple? Arguably. Not a viewpoint that will make me popular, I imagine.
Anyway, before I begin to sound like someone who knows what he's talking about (I'm not, and don't), I'll get to the point. I like describing things, I like to tell my readers that the sunset is painting the distant horizon in deepening shades of pastel violet; I like to play with commas and punctuation, crack open a thesaurus once in a while and avoid the mundane. I love imagery, I love carving a story from a hunk of unformed language with the grace of a sculptor. Or trying to, at least.
Succinct sentences have their place. Like there, for example. And there. But what makes authors stand out is individual style: Steven Erikson and Robert Jordan are famous for writing in the same blanket genre (which fantasy undoubtedly is), but they're very different scribes. The late, great Jordan was a perpetrator of the "info dump", often accused of spoon-feeding readers with info and exposition, where as Erikson will likely be buried with the cliff notes to The Malazon Book of the Fallen. The point is that one man's purple prose may be another man's perfect pitch, one man's info dump is another man's welcome elaboration.
Again, not pretending to know what I'm blathering about, just tossing out some jabberwocky in the hopes that some of it makes sense. What I think I may or may not be trying to say is that I will be accused many times throughout my career (I say career on the off-chance that I eventually have one) of using purple prose, info-dumps and being generally far too free and easy with the adjectives, and if that shrinks my target audience, so be it. I feel that working too hard to change my style would be to remove the positives (of which I hope there at least an equal amount) as well as the negatives.
Instead I'm trying not to focus on such concerns and instead worrying more about the content of the story, the characters, the thread of the plot, the flow of the narrative (purple or not). Will overuse of imagery and adjectives put off critics? Undoubtedly. Will it put off readers? Perhaps. But only perhaps. Some readers just want a good story, regardless of the colour of the prose.