I have a 4500-II, and your friend is correct in that there is no way to align the stages, short of shimming them - and I'm not even sure if you can shim them. However, they are rarely out of alignment, if ever. Bruce Barnbaum has 7 of them (yes, seven), and I believe John Sexton had a couple, or perhaps as many as four. Ray McSavaney, to whom perfection is just barely good enough, has a 4500 XLG. I think if these guys use these enlargers and are happy with them, then I think you will be too.
The enlarger is very well made, very sturdy, and it's construction ensures that everything is in alignment. Its design precludes going out of alignment. You don't have the flexibility of adjustable stages (say for perspective adjustment), but that lack of adjustability ensures that everything is always in alignment.
While it leaks a bit of light around the negative stage, that's a minor problem when you consider the quality of the enlarger itself. The light leaks are easy to fix. Not even an issue, really.
Pick one up - you won't be disappointed.
Regarding alignment, if you mean making sure the head is aligned to the base, I use mirrors. One in the negative stage pointing down, with a hole. One mirror on the base. Look through the hole and adjust the column until you only see one hole, and not a curving line of holes. This really only makes sense if you wall mount the column, as I have done. If you mount the enlarger on the supplied base, then use the same procedure, but shim the base. Shouldn't be an issue, really.