I played Heimer a lot last night, 4-5 times, and a few observations I had:
1) One point in Turrets then prioritize R>W>E. Unless you're really good at maintaining a pushed lane and you have an aggressive counter jungler to keep the enemy jungler busy, turrets just push your lane really hard and you don't have an escape.
2) Get to lane ASAP and start planting turrets. You can get all three up before the minions get there. This strat would really work in a counter-jungle strategy or as a support. I can see a player running bot, going into the enemies bush and plant three turrets and smack someone around. Kind of like a Shaco support tactic.
General strategy that really helped me was planting a turret right behind the minion wave and just poke with autos and W and E. You don't want to push the lane out.
3) I never really was mana starved which was nice. When I started top my last game, I went 9/0/21 for CD redux and mana regen and it seemed enough to stay in lane. I went Shield into rushing Seekers. I did really well against Xin Zhao with this strat. Ended up going 3/1 and killing a Xin Zhao/Noc gank 2v1. Runes I used were MV quints, hybrid pene/mpen marks, armor yellows and AP/L blues.
4) Turrets suck versus Nasus after mid game, all you do is give him free Q fodder and they do shit for damage. Turrets are awesome versus squishy targets. I had a Nid W into three turrets while we were seiging their base. Chunked her pretty good.
5) Your Upgraded E can be a real pain in the ass to land sometimes. Three times I had some fucking champ charge in, under my E and snag me. If you're using defensively, cast at your feet. It works really well.
6) W is really hard to aim sometimes. That focal point where the rockets come together is really fricken small. You have to get used to aiming a good amount of distance before your target. Alternatively, you can really squeeze W rockets through a small window in a creep wave and fuck someone up. It also takes some getting used to if you want to shoot a large fan of rockets. It can get a little wonky moving your mouse around at a short range.
Spectral Wriath and spell vamp in general is shitty on Heimer, don't bother. I really didn't notice a difference.
Build Order Top vs. AD:
Shield > Seekers > Morellos > Boots > DFG > Rabs etc.
Build Order Mid vs AP should be a typical build, but I would rush Athenes and then DFG (assuming 10% CDR in masteries) for 40% reductions. 40% CDR really helps because you want to be able to drop turrets and your ULT as much as possible. Turrets really do help late game inside a big group fight. They had just enough extra damage because people often forget them.
They only changes I wish Riot had done would be to give Heimer a larger turret placement range like Zyra's seeds. It really sucks getting turrets out in a group fight.