You would get eaten up on the freeways around my area on a 250.
Well, CDailey did specifically mention the Ninja 250. From personal experience I can tell you that the Ninja won't win any 70+mph drag races, but if you're not paying attention and just passing cars you could easily find yourself doing 90. Keep going, though, and the engine will hit a brick wall, running out of steam around 105mph. Hey, 36hp can only take you so far.
That said, keeping up on the freeway is absolutely no problem. However, between the seating position and the vibrative parallel twin, long rides can be trying. The most I'd do in one sitting is 2 hours; I don't know how that compares to the typical rider/bike.
Now, obviously I'd be one to recommend a Ninja 250 to a beginning rider.
They're affordable, plentiful, nigh bulletproof, safe enough for beginners, sporty enough for experienced riders, and they went unchanged in the united states for 20 years so parts availability is through the roof. They also tend to be in high demand, so if you'd like to just buy one, learn to ride, and then move on to something bigger, finding a buyer won't be much of a problem. I don't know how the release of the new Ninja 250 has affected this, though.
The following website is a great resource for more info on the bike:
http://www.ninja250.org/
Otherwise, I always recommend an older 500 or 600cc bike in whatever style (sport, cruiser, standard) you prefer. If it's kinda beat up, that's good; it won't be as heartbreaking when you fall or drop it (and you
will).
I'd recommend other 250s but there aren't really any in this market that are worth buying over the Ninja. I liked the Honda Nighthawk 250 I rode in the MSF course, but I haven't heard good things about them.