I seem to remember someone saying (Robb I think, although Spoon has definitely said this as
well) that the micro levels are almost perfectly designed to teach you the basics of good play at all stages of a hand.
So, 2nl teaches you the basics of good play Pre-
Flop. At 5nl you have to be
able to play decently on the
flop. 10nl you need good
turn play to be a winner. And 25nl is the first
level where you need to play reasonably
well on all streets to make any money.
From my experiences so far (at present rate I'll hopefully be at 10nl in about a month) I think this is very accurate.
With specific reference to 5nl I found when I moved up that whereas beating 2nl is simply about selecting good hands preflop, hitting, and then pretty much mindlessly value betting down to the
river, 5nl requires you to make slightly harder decisions on the
flop, where you'll get people playing
back at you a little more and so on. Once you get used to this, it becomes fairly ABC.
Always bear in mind of course that progress can still be painfully slow,
don't fall into the "it's 5nl, why aren't I beating it for 20ptBB/100!?" because (believe me) that will slow you down even more.
GL at the tables man.