I agree, I'm just thinking about forward and cross-compatibility. I am finishing up a complete CSS/XHTML rehaul of my big store which will accomplish that, so I suppose it's all in your priorities. I don't want to miss a sale if I can help it! I also know that google considers keyword spamming image alt tags as a no no.... and I'm not taking chances to get hit with the big fat PageRank 0 penalty!
Content is king with the search engines, and it's pretty hard to trick them these days without being caught quick and being sorry for a long time. Good optimization combined with good content produces excellent results!
(and BTW, I use my cell to surf sometimes, and it's not expensive at all. In fact, with Verizon, I can use my regular minutes as internet time---on weekends---yep, it's free
)