Slopes are my preference. They add more dimension. I don't think the positioning of the stones are bad. Perhaps you can try other arrangements (with pics) so you can have options that others can vote on to help you?
BTW, I want your lily pipes!
Are you getting an inline heater for your fauna?
If you do get some lily pipes, i recommend the Calaqua ones from GLA. very nice quality. Probably on par with ADA (never really seen ADA ones so I can't be for certain). The ebay ones tend to be made of thinner glass and are easily broken. I got the CalAqua nano pipe set.. i think it was around $70 or so? cheaper than ADA.
and nope.. no inline heater right now. maybe later. it'll be primarily a shrimp and moss tank.. and i think they both like colder water. my house is pretty well heated.
i'll move the rocks around and take some pics to see which way looks best.
i love your tank though. i can't really afford/have time to do co2 though.. so no Ray 2 or co2 for me right now.. maybe later on!