- you make a big investment (upwards of $2000) and it motivates you not to give up
- it sounds good, it looks good, it even smells good (rosewood, mahogany, spruce, ebony - that kind of thing). If you're into guitars (or simply beautiful things) it's hard to put down and you find yourself spending more time with it than you'd initially planned. And that's the single best thing for getting better at it :)
- you get no excuse (like, "it's not the real thing, it sucks, that's why it doesn't sound right even after many hours of practice"); it helps to remove doubts and concentrate on practicing
- if nothing else, it will make a decent long-term investment (high-end guitars tend to depreciate in the first years after the purchase and appreciate afterward). Some people even claim that it's a better investment than real estate, but I don't know about that
Ask somebody to play it for you, ask their opinion of how easy it is to play, have it set up by a good guitar technician... And keep on picking :)
Also, somebody mentioned justinguitar.com; it is a great site; the guy is a great teacher and a wonderful guitar player. It's got a bunch of theory lessons, but also lessons where Justin picks apart famous guitar songs and teaches you to play them in a "dumb" way - some might say it's cheating, but it surely helps to keep the fire burning when you can learn a tune or two without pulling your hair out trying to transcribe without the required experience (it's very hard, although that's what every guitar player should try to learn eventually).