Oh no, it's this again!
I don't see all that much conflict between the perspectives posted so far, really, besides a difference in view on just how concentrated is concentrated enough, which is one of those questions nobody is going to agree on. The main dividing issue is the nimitta thing, which the upakkilesa sutta is often drug out to support, though as far as I can see that sutta doesn't seem to be saying anything about the practice of absorption in particular, but something a little different, the development of iddhi of a variety as Modus suggests seems to make sense. Additionally as far as I have seen, perception of beautiful visions etc. isn't really associated with the development of jhana in general in the suttas. I'm willing to make the assumption that if it were vital, it would have been made a bit more obvious.
I think the core of this jhana issue comes down to which texts the individual decides to take as authoritative. Some people like the suttas, and their perspective is colored by that, some people like commentary, abhidhamma, and the same thing applies. There's got to be an agreement on that before this will be settled, and I don't think that'll ever happen.