Well, I might have somewhat of an answer. Googling some more this evening I discovered AO Smith is releasing a new 96% efficient Vertex. I went to their site (http://www.hotwater.com), but they don’t have it listed under residential products yet. They do, however, have both the spec sheet and manual in their literature pages (http://www.hotwater.com/lit.html).
The original has a 6 year tank and parts. The new one has a 3 year tank and 1 year parts (found on the last page of their respective manuals). Perhaps they learned they were too optimistic with the original or perhaps they are not as optimistic with the new model. Could be either I suppose. Haven’t seen a price yet either.