I have a Maxon OD-808, which is identical to the TS-808. Its a very nice pedal, very quiet, but not real powerful (the 808's just dont have much gain, compared to other pedals)
It replaced my stock taiwan SD-1. That thing had a nice creamy sound, but it was so noisy it was unusable. Cheap components. I hate Taiwan Boss.
Although, I messed around with the Ibanez TS-9 and TS-808RI, and I found the TS808 re-issue to sound identical to my Maxon OD-808.
But, to my surprise, I flipped on the TS-9 and LOVED IT. The 808's have a subtle gritty, sandy sort of texture. The TS-9 doesnt have this, its very smooth, and I think it sounds more like a tube amp then the TS-808. Its also got a bit more gain (I think) and its much tighter and more defined, especially on the high end.
I dont know why people want to mod their TS-9's into TS-808's. There are just too many people trying to cop the SRV tone, I guess thats why. I dont even think SRV has that good of tone. You can get it instantly with the maxon: Dime the Level and Gain, get a tube amp with a clean channel and a strat with decent pickups, and there you go! Warning - Chops required!