I was also conflicted whether or not to spend the extra $50 on 3G and decided since we have wifi most every place we tend to congregate, it wasn't worth it.
When will you need it? Mainly to d/l books, right? And who knows what the market will look like in 2 or 3 years when the K6, Nook 6, Sony PRS-xxxx is out. It may be time for an upgrade at that point and then you'll have a better idea of what you need/want.