I'd like to mine at a p2pool, but I'm wondering if the 'dust' issue I've heard about with other coins is still there? I'm only mining at 380kh/s, so I'm probably getting loads of small payments. Is this gonne rise the fee's for me with Vertcoin?
Run your own node or use
http://vtc.royalminingco.com:9171/static/ for now. That node is simulating miners as if they were running their own nodes. You can have less variance if you force diff lower, but you should see shares more often than other nodes if you leave it in the default setup (just connect with payment address).
If you want, look at the Day graph for other miners with a similar speed to you and then you can see what their share chain value history looks like (in the 2nd graph). These payments are small (if you only have 1 share during a payout) but not crazy small.