No, I didn't forget about this. I've been looking into it here and there and then debating whether I should just point you to the resources I'm looking at or try and summarize the arguments and how much detail etc.
Guess I'll do a little bit of each.
B.B. Warfield has a good but long article rebutting the argument against Petrine authorship by Edwin Abbott. It deals primarily with two arguments unique to Abbott: Peter couldn't have been the author because if it's unintelligent style and because it borrows from the works of Josephus, which requires a date too late for it to have been authored by Peter. But Warfield also mentions some other sources and ways we can account for other objections to Petrine authorship in the first 1/3rd of the article.
For example, to the claim that the external evidence for the Epistle is insufficient, Warfield notes that 2 Peter is quoted by many before Clement of Alexandria and refers to an earlier article which argues this (Souther Presbyterian Review for January, 1882, pp 48.) and notes that “Clement wrote a Commentary on it as a part of a series of 'concise explanations of all the Canonical Scriptures.'”
The argument is made that 2 Peter is dependent on books published after Peter’s death. Abbott lists the Epistle of Clement as an example of this, but Warfield points out that Clement is also known to have borrowed from other sources (Hebrews) and so he may be borrowing from 2 Peter rather than vice versa (and we know of many other writers who borrowed from 2 Peter: Origen, Clement of Alexandria, Irenseus, Theophilus, Melito, Hermas, Justin, Barnabas).
Warfield argues that we can establish that Clement borrowed from 2 Peter simply by comparing the parallels (Clement 7.1 and 2 Peter 1.12; 3.1; Clement 7.5,6; 11.1 and 2 Peter 2.5-9 etc… you can consult the article for the full list).
Regarding stylistic differences between 1 Peter and 2 Peter I agree with what Charis has said. Warfield adds a good quote by Reuss that shows the slim evidence upon which the judgment is made: "the two Epistles are too short, have to do with wholly different circumstances, and especially present no direct contradictions; only if the Epistle is on other grounds proved to be ungenuine, can [these stylistic differences] also be brought into account.”
Other sources account for the difference by use of other source material: “…preformed material makes up at least one-third of 2 Peter and that other verses, although less easy to identify as such, may also represent traditional idiom (e.g. 2 Pet 1:2,5b-7; 3:18). That is, like other New Testament letters 2 Peter, although a carefully formed unity, is composed to a considerable extent from preformed materials that are somewhat reworked to for the purpose of the author” (The Making of the New Testament Documents 133).
The Anchor Yale Bible Dictionary lists the following as evidence against Petrine authorship: “…the conventional Greek virtues encouraged in 1:5–7; the notion of death as a ‘putting off of the bodily tent’ (1:13–14); identification of the realm of the dead or “hell” (RSV, NEB) as “tartarus” (2:4)…”
But it doesn’t take much work for us to see that this evidence isn’t very weighty. For example, I can think of lots of other places in the NT that speak of knowledge as a virtue or at least as something commendable, same with self-control, brother affection, etc. The Bible elsewhere uses Greek terms representing the after life (Gehenna for Hinnom) so it doesn’t seem that unusual as to deny Petrine authorship. Warfield says something relating to this issue in another context in the article I mentioned.
Claims like "there are theological differences between 1 and 2 Peter" may sound weighty on the surface, but when we look at exactly what these differences are supposed to be we can usually explain it by differences in situation and the own critic's bias (AYB mentions German Protestants reacting negatively to it's reliance upon tradition; we have an example of similar misguided bias in Luther's rejection of James).
The resources I'd suggest are Warfield's article which you can find
here (link), I think you can find one or two of the other sources he mentions h
ere, the Word Biblical Commentary (Bauckham believes the testament view, but also that it was obvious to the original audience), NIV App. Comm., and New American Comm. The New International Comm on NT is always an excellent place to go, but they haven't released the comm. on 2 Peter yet.