The competition is becoming slightly more difficult overall in SNGs, so the importance of having some type of reads on the other players has also increased. I've talked with plenty of poker players who tell me they don't bother taking much notes - instead they will watch a movie, browse forums, talk on AIM, and do everything else not related to the game. If you want to improve your game, one of the first steps is concentrating on the games themselves.
Now how do you get reads in SNGs? With SNGs you can get reads a few ways.
The old-fashioned way
During early stages, the ones who have close to the default starting chips until 30/60 or 50/100 likely are somewhat tight. Whenever there is a showdown, look at the hand history to see what position players limped, raised, or called a raise with their hands. Anyone who min-raises after limpers you should immediately peg as a donk, especially if the hand is something like AT (make note of other donktacular moves as well). Also, late game, make note of any all-in push and call so you have a better idea of what they'll call and push with in different situations.
Of course, if you're doing reads the old-fashioned way, you won't be able to spend as much time watching a movie, chatting on AIM, and browsing forums while 4-tabling. When I'm playing, I have an away message up, music playing, and nothing else going on. Maybe during early stages I'll mess around a little bit, but then try to catch up later.
PT and PAHUD "reads"
PT and PAHUD will give you a rough idea of their tightness/looseness. It isn't as accurate as with cash games since people play differently per blind level, but you get the idea. If someone has 60/40 stats, you can certainly peg them as LAG. If someone has 15/7 stats, you can peg them as TAG or rock. Inbetween... look for the fish with stats like 33/3.
I do all of this while 3-4 tabling with little trouble. Me checking the hand histories and making notes also keeps me busy early on so I don't get bored and lose concentration