As it's been said, nothing wrong with using reasonable ammount of 90deg fittings in loop in some cases for simpler tubing routing, it's bad if All fittings are such. In last pics posted by SpuTnicK i counted 14+12(14-2 for inlets)=26*90deg fittings. It WILL impact flowrates in noticeable way.

2skinnee: can you do close-up shot on inside walls of one water tube? - are those with extra internal "fins" for better heat exchange?