First service, or any service does not have to be done by a Suzuki dealer to keep the warranty valid, you could do it yourself and still have the warranty valid, as many do. Yes even the BMW's can be done by their owners and it has no effect on warranty. If your dealer stresses that the bike needs to come back for service to be done there, it's a sales pitch for them.
John
PS, bikes with too low of mileage on them can be a bad thing, they could have not been broken in properly and not been ridden enough to seat engine components properly, as well as everything else on the bike. I feel much better with 2,000 miles on a 2011, but would I buy it with 300 miles on it, probably yes.
John