I'm definitely of the opinion that goggles are an area in which you should never skimp. All the equipment in the world is worthless if you can't see where you're going. That being said, I've never been a spherical devotee. Not saying they're not great goggles, but I don't find the spherical shape of the lens to be crucial. I had a pair of Oakley A- frames (the classic spherical) for a season. I liked them, but they got stolen. After that, I bought a pair of anon. Figments, which I have had ever since. The anon.s are not spherical, but the quality of the anon. optics has me sold. The original lens in my anon.s was a gold chrome lens. Having taken pretty good care of my goggles, I have the same lens 5 years later. I also have persimmon, rose, and yellow lenses for them. This offseason, I bought a second pair of figments, to cut down on lens changing.
Long story short, always buy good goggles. Spherical goggles are always going to be high quality, but you don't have to go spherical to get a top notch goggle.
Oh, and the reason my lenses are still unscratched after 5 years is I'm obsessive about proper care. I only use a goggle cloth or a skigee to wipe them off (never my gloves, bare hands, or god forbid tissues), I always take them right off my helmet, wipe them with the bag, air dry them, and put them right back in their bag. They never sit on top of my helmet when my helmet isn't on my head. Meanwhile, I see people 'saving' money on goggles by buying $30 Gordini's, which they trash and have to replace within a month. So by the end of the season, the 'thrifty' guys have spent well over $100 on goggles, which ends up equaling what I spent. But next season, my anon.s will come back out of their bag for another year, while they're back in the shop buying yet another pair of goggles.