I'm not planning on getting a 3DS. It's mostly a money issue. Not that I think it's not worth it... I just don't have the expendable income. I bought the last 4 Nintendo launch products, too, so this will break my streak. (Wii, DS, GameCube, GBA)
As for hardware revisions, it's generally not a factor for me. I did get a GBA, then a GBA SP. This is because $99 was totally worth actually being able to see the game I was playing. But I still exclusively have my DS Phat. The Lite doesn't have $129 worth of upgrade. It's just slightly smaller. The DSi just let you download some crappy games... I've never heard of any DSi games that are really must-haves (unless I'm just out of the loop?). I'm not angry that Nintendo has released other (better?) versions of the DS. Ultimately, if I felt they were worth the price, I'd buy the newer version and I'd be happy because I chose to buy something that was worth having. Or, I'd keep enjoying the version I have, knowing that keeping my money is better than buying something that's not worth it.