So far so good, there hasn't been much load-shedding to test them properly. So below isn't a definitive review;
I charge them till 14.25V and disconnect at 11V, never ran out of charge till now (may be 3 hrs at 1 kw usage). They bubble more than I anticipated, usually take one liter every month or 250ml/battery. Also its documentation (single page) stated to charge at 9A and quick charge at 15A. This is lower than most batteries. I've put the same settings in UPS, Utility supply at 10A, solar at 14A.
For UPS purpose one should opt for deep-cycle (50% DOD, depth of discharge) instead of regular starter batteries (5% DOD). However most of the batteries I found in the market were second hand and sold as new. So opted for safer/cheaper option.