I understand your frustration with this and yes, Telerik needs to work on their expectation game, but believe me, it's worth the wait and what they do release tends to be great! So stick in there
Those of us who were in on the Beta testing of v3 were there for a lot of those delays. I don't think we felt you were trying to airbrush reality or mislead us, but I also don't think you guys build in nearly enough time for the unexpected. I would suggest that you should have internally planned for a release of June 21st, but announced to the world that you would release on July 15th (for example). If you make the June 21st date, everyone is stoked. If you have to push it a week or so, no problem, you're still WAY ahead of schedule.
Under sell, over deliver! If you order a Dell, they tell you it'll ship in 3+ weeks, but it usually ships within 3-4 days. People are always psyched to get their computers soooo much sooner than they had expected and it's very rare that they ever ship after the 3 week period, so people are never disappointed.
Does that make sense?