I've backed 17 projects so far on kickstarter, almost all of them games. To date, I have received 13 of them. A few late, but not egregious. Of those still due, only one is at risk. It is 18 months late, but the kickstarter has keep us informed the entire time -- delays have been due to an inability for the factories (on the third one now) to meet the specifications of the prototype consistently enough to make the product functional. Poor guy has mortgaged his house for the project.
All but one of the games I kickstarted were later available for public purchase. I could have waited until then and got the same product. By supporting the kickstarter, I did get some additional items for the games as a bonus, but for the most part they were not compelling reasons to back a game ahead of time instead of waiting. Some of the extras in the games I simply have never used -- they were nice, but unnecessary. The ONLY exception to this was my backing of the Dwarven Forge products. These products are generally so expensive to begin with, getting extra pieces as a bonus for stretch goals is a great deal. Additionally, Dwarven Forge kickstarter seldom translate to public availability after the products are delivered. So far, from what I've observed (I've backed three Dwarven Forge KS for far) is that they produce enough to meet the KS orders, but very little left over for the general public. Usually, within the year, they have restocked the new stuff for everyone else to purchase, but the extra pieces are generally not available.
Only one game I backed has been delivered only to the backers and not enough was made for retail sales. I and my family enjoy the game a lot, but we also recognize that it is a niche market with limited appeal. I had to go to great lengths to get a second copy afterwards by buying an extra copy from another KS backer.
So far, only once have I backed a game that once receiving it thought it was WAAAY overpriced for what was provided. I think they were going for an over-production feel, which came with an over-production cost, but it really wasn't needed. Especially when errors were discovered after the fact and addendum. I enjoy the product, but suffer a little buyer's remorse over it.
I've seen many projects on KS that look really great, but I decided to pass -- everyone has to have their own criteria over what is worth backing or not. Many of those projects are backed and sold publicly. Some I bought, some I didn't. Others did not meeting projects goals. Sometimes it was obvious (poor concept, etc), sometimes it was a shame (it looked really cool, but....)
I'm been backing a project over at Idiegogo. It's a different interface and backing process than Kickstarter. Some project designers like its flexibility over Kickstarter. One of my favorite projects moved from KS to Indiegogo this year. So far, I am not sure I see a difference in the quality of projects from the two sites. I've seen more polished presentations at Kickstarter, but that is just a salesmanship issue not a project or site issue.
Anyway, my experience with funding projects.