I am seriously pondering this same (or very similar) question that coherent finds himself considering. I think I may go for the Alpha rather than the X series with mine though, simply because of the larger size, leading to better heat sinking...resulting in longer duty cycle/on times. However, I may even go back on my word here and decide to go with the X series just because of cost. I'm considering everything between 45mW and >100mW. My Laserbee is on the way, so things are really getting exciting now, to the point where I can finally get to some *real* projects. Still, I too want to have a laser that is handy to whip out and test out in the foggy yard out here in the country. Lately it has been raining almost nonstop and with my labbys I'm tethered to a cord.
Getting back to the main point. There are several areas where it just wouldn't be logical not to go for a higher power, when the difference is only that of 30 USD or so. This is just a difficult decision, I may even decide to spend the cash on parts rather than a very expensive toy, since I tend to get the most satisfaction out of experimentation anyway. We'll see.
-Brett
*edit* Ok, if I end up getting the X series...I'll go with the x75, since jumping up to the x100 is a 60 dollar leap just for 25mw or so....but dropping to the x50 gives up 25mW at only a 30 dollar savings.
With the Alpha, I reason that the 65 would be best since jumping to the 85 is a 40 dollar leap, and jumping to the 105 is about a 90 dollar leap. Again, dropping to the 45 only saves 20 dollars, so it's better to stick with a >65mW laser with the Alpha and have a nice visible beam for those foggy nights.
That's the way I analyze it at the moment...maybe I put the "anal" in analyze, but I have a lot of laser parts to buy this year. I may forget about getting a Nova altogether, but I have a feeling I may regret it.