Kalonline is one of the best if not the best FREE MMORPGS. Highly addictive, the need to level is always there.
As for the Graphics: The game requirements aren't to high, if you have a smooth XP boot you'll probably be able to run it on the lowest lvl of graphics of course.
But if you have a sweet game PC the game can be quite surprising: High grass that is moving along with the wind, nice textures, ...
But graphics aren't so important its the gameplay which makes a game addictive or not.
The problem with Kal Online is that its an bee VERY confusing in the beginning. So I advise all the new players to first read some guides on http://www.kalhq.com or http://www.jainesoutpost.com/index.php?set_game=1.
Once you get how it works etc. the game becomes highly addictive, you always want to get that one level higher to be able to wear that armor, or your new weapon or to meet the requirements for a guild.
There I said it GUILD the real fun begins around lvl 30 when you're probably in a guild, you start going into party's, you get to know people very interesting.
Something bad: the sound, the same tune, OVER AND OVER again. But its easily turned off so not a real problem.
So, its not the best MMORPG but certainly of one of the best FREE MMORPGs.