I had a solar water heater in AZ with an 80Gal tank and LOVED IT! I have a 50Gal tank with a booster electric tankless in ND and it's OK after about the first 5 minutes in the shower (software is very slow on tankless for safety reasons) I wouldn't recommend a downline tankless, put it upstream of the tanked water heater (though in my situation this was alot less cost efficient).
10/1/11: Bought the perfect house;11/1/12: 10k & 200 hours into the perfect house; Floors are done and cutting up the cement for the new bathroom that wasn't actually plumbed like the seller said it was; 8/1/13: 30k & 400 hours into the perfect house that only needed new carpet and a coat of paint...
12/1/13: 35k & 500 hours I hope it ends soon
02/1/14: 37k & 550 hours and the inside may be finished soon.