Marc, I first bought a scanner of the general type you pointed to. It was very fast and very convenient... but the quality was truly dreadful. Happily (!) it had a light leak as well and so I was able to return it with free return postage!
I next bought a Plustek 35mm scanner, which you run (like all better scanners, AFAIK... drums etc aside) tethered to your computer, with a variety of scanner software. I have scanned thousands of old slides, black and white or colour negatives. It's a little fiddly, but you can set a scan going and then go back in the next advert break (or whatever), check and advance to the next frame. It works very well for black and white negs, reasonably well for most slides (although old Kodachrome, any Velvia and some Provia slides can cause problems with shadow areas, and sometimes weird colour casts). Colour negative film can be more problematic because of the underlying orange colour of the film substrate. There are various ways of fixing this, often through film presets in the controlling software, and they work variously well. Sometimes I get really good results, sometimes I get colours I just don't like. I'm not good at fixing colour casts in later PP (eg Aperture).
For my current 35mm stuff, I tend to send C41 colour and C41 black and white to Photo Express, as Adrian does, as they do a "medium resolution" scan (2000 dpi, good for a 6"*9" print) for a very good price (£4.50 per film with the TP discount) with their processing, and their quality has been excellent for me. Most other companies are quite expensive for scanning; AG is one of the cheapest, IIRC, but they have also been much slower in my experience, so 35mm black and white or slide tends to go to Peak and I then scan it at home. It will normally be scanned the day it gets back to me.
I've only just started on 120; I bought a V500, mainly to scan my father's legacy DufayColor transparencies, but also to scan a few of my own. Generally I understand the quality of 35mm scanning on the V500 is less than scanning on a Plustek; that said, many on here use it for both and get perfectly satisfactory results with it. I've still got a few hundred packs of colour negatives from when our children were growing up to get through, so I'm not planning on selling my Plustek yet.
I've had process and scans done by Asda, Boots, Max S and Snappy Snaps, and the general quality has been variable. Somehow I just don't like the results; it's not only low res but usually over-sharpened.
Paul (@
PMN) drum-scanned some of my father's DufayColors as an experiment, and the results were truly wonderful. They came as >100 MB TIFFs, though (but I could probably have asked for JPEGs), and I wouldn't want all my scanning to come that way. I did get a quote for doing the rest, but given the number I had, it was too expensive, so I perservered with the V500 and the results were good enough to make a photobook from them for my brother and sisters.
I'd quite like to try UKFilmLab, as RJ does, but by the time I've finished a film I'm quite impatient to get it back, and their 10-day turnround puts me off. It would be really good to get some exposure and other feedback from them, though.
Not sure this helps much, but my advice would be: DON'T on any account buy a scanner like the one you pointed to; if you're going to stick to 35mm then a Plustek or Reflecta scanner would be good, but if you see your future including medium or large format, then a V500 or V700 would be appropriate. Oh, and I'd suggest getting Vuescan Pro scanning software, as you'll then be able to use the same software on almost any scanner you buy in the future, including the one built into any all-in-one printer you've got!