I have not tried that service but maybe it's worthwhile for you to send them a couple dozen slides and see if you like the results. The "camera store" scans I have gotten - i.e. develop & print film + scan images to CD have all been totally useless - big dirt specks, uncorrectable color problems (I suspect they were scanned in 8- or 12-bit color, not the 24-32 bits you need to capture high quality color rendition).

I have an Epson flatbed 2400dpi scanner that produces very, very good results from negatives and slides. The problem, as you point out, is that it can scan only a small handful of images at a time. It's also slow and tedious. The Nikon auto-load slide scanner would definitely be faster but they're not cheap.

Given you have a finite number of images to scan and how tedious it is to do, I'd be very inclined to use a service like the one in the link -- if the results are good and the price fair -- rather than buying an expensive scanner and doing it myself.