Re: 6l60e
The new C6 'Vettes are available with the 6L80E. Also the STS-V and another Caddy. The new GM900 platform trucks will have it available (new Tahoe's, up-coming Suburbans and the rest of the pickup line).
If you read the literature, it ought to be a good transmission. The gear ratios are nicely spread (not the super wide ratio drops that the 700R4 provides). Once they become readily available and product support gets cooking on it, it will be a viable choice. I expect that it'll make the 4L80E swap look like a bargain though.....
'JustDreamin'