I've got one of the 30mm eyepieces and for the outlay it's awesome. I think someone a while ago pointed out that it's the same as an eyepiece from moonfish. On the Moonfish website there is a copy of a group test of wide angle eyepieces under 500 pounds.
http://moonfishgroup.com/catalog/ima...Y_06_98-98.pdf
http://moonfishgroup.com/catalog/ima...Y_06_96-96.pdf
Interesting reading, it's what finally made me get one. If the 20mm and the 15mm are the same as the 30mm then go for it.
Gareth