A couple things to consider on an '06:
Pro's:
1)You can do TBS's(Throttle body Sync's) and idle adjustments yourself, which will need to be done after a valve adjustment, provided you're a do-it-your-selfer. The Suzuki dealership is way overpriced in the town in which I live, so this is important to me.
2)The '06's are a bit faster than the '07's and newer.
3)The '06's are pretty well de-bugged. Not to say '07's + are not, but when new changes are introduced into a model, sometimes new problems can be introduced. My '06 has ran virtually flawless.
Con's
1)The '06's do not have ABS(as you know). Although I think ABS is a great feature, I would not trade my '06 for it, because of the aforementioned mechanical reasons, & because I would probably have to add some cash to the deal.
2)The gas mileage is not quite as good as on '07's and newer, but not by a lot.
I'm not sure what the blue book price is on an '06, but at $3600 & 21k miles, if it hs been well-maintained, I'd say it was a steal, unless you think it's likely that another one will come along in a suitable length of time. At 21k miles, it may be nearing time for a valve adjustment at about 26k mi, if one has not been done already, but this can vary.
Good luck.