Kamran, i bought a 0.8 ton last year and it is going great, i bought it around 20k, and yes room cooler in karachi is not a good idea, i don't have any experience of it but people who use them are happy, they are better than the fan alone.
I went to buy another 0.8 or 0.75 ton unit to replace one more 1.5 ton, but couldn't find any, what i found was a 0.75 ton window type Samsung without any Warranty, did not buy it because window type 0.75 ton can never replace a 1.5 ton split type, window type are less efficient.