They have a point, but it is OEM customization of Android that creates these delays, not Google.
Two months later, and we've now seen Android 4.0 more than double in market share, while Jelly Bean, still available on only a few devices, has reached 0.8 percent in only about three weeks.
The info comes straight from Google's own website.
Not only that, ICS' 15.8 percent means that it is now the second-highest utilized Android version, behind Gingerbread (Android 2.3) at 60.3 percent. ICS is barely in second place, as Android 2.2 (Froyo) is in third at 15.5 percent.
One Jelly Bean-only feature that has drawn attention is Google Now, a tool that has been compared, favorably, to Apple's Siri. However, as it is limited to JB handsets, it is not going to be adopted quickly enough unless one of two things happen: a) Google separates Google Now from JB and allows downloads in Google Play, or b) OEMs begins shipping JB in bulk.
The first of those is probably unlikely to happen at all. The second of those, if the trend shown by ICS continues, will take a long, long time.