I noticed there has been a few G15 guides been posted, so heres my 2 cents.
If like me your a bit cautious when it comes to using bots, you can set up your own macro bot using the G15 macro keys. If you change the options so that it record time delays between button presses, you can set up a macro which will kill a certain mob. This is really useful for either just being lazy and only having to press 1 button to kill, or if you set up the toggle option, you can leave this running while you go afk. This is really helpful for gaining xp and/or influence.
There are a few downfalls though, one of which, you can't pick up the loot if you go afk. But if you just want some easy xp, it's really handy. Another issue is obviously it only does what you tell it to, so if a unexpected patrol group comes along, you may get into trouble. That's why it's best to stay in an area where there are mainly static mobs that you can aggro as you want.
I've been using this in the 100k farming spot mentioned in another thread. Just sat my character nearby to one of the spiders that spawns, press the toggle macro, and done, easy xp. And you can even edit the macro to input pauses if you know you'll need to rest in between mobs.