Bargain on Rockwell SoniCrafter

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I've never used a variable speed model - and I assume you haven't either - but here are my thoughts/assumptions.
1 - Now, this is probably the least important reason for considering the variable speed unit, but I'll toss it out there just to get it out of the way:
AFAICT, every company offering a multi-function tool, ranging from the lowest end (HF) to the original (Fein) offers a variable speed unit. Wen, Klutch, Dremel, Rockwell, Bosch, etc. In fact, I'm pretty sure that most these companies don't even offer a single speed unit. Sure, it could all be marketing and "keeping up with the Jones's" but it seems to me that if every single company offers a variable speed unit, there must be a market/need for them.
2 - I have a couple of palm sanders. Using them in corners is a pain because they bounce around too much. The variable speed multitools might solve that issue by running at a slower speed for more precise control in tight spaces.
3 - Plastic: I copied this without permission from http://diytoolshop.info/dremel-variable-speed-multi-pro /
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A: If you have a variable speed tool, select the 1 on the MultiPro and 5 in the Professional. These positions correspond to the lower speeds. If the work in acrylic plastic and is its main application, we would recommend working with additional control and Professional tool to consider a single-speed tool with a separate dremel variable speed multi-pro control, as the dremel variable speed multi-pro control pedal (No. 221 dremel variable speed multi-pro. ) A single-speed tool with independent speed control allows the tool to operate at speeds even slower than the lower speeds the variable speed tool.
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I once used my single speed unit to cut the dividers out of a DeWalt drill case so I could use it for a brad nailer I bought. While the cuts were easy, the tool did melt the plastic requiring some cleanup afterwards. I think that if I could have slowed the unit down somewhat I could have cut the plastic with less melting.
I have also seen indications that different speeds might be desirable for soft vs hard woods.
4 - Just as we often use our drills, sabre saws, reciprocating saws, etc. at different speeds based a specific situation, I have often been in situations where I have said to myself, "I wish I could slow this thing down just a little. I think I'd have more control." Sometimes it was just a desire to start slow and then ramp up the speed and sometimes it was situation where I wanted to use a lighter touch at a slower speed for more precision. My assumption is that the "jerking" you are concerned about could be compensated for by using less force.
Again, having never used a variable speed model, I can't say for sure that the above reasons are valid. I guess I should just buy one and see. For $45 all of my questions would be answered.
Anybody want to buy my single speed unit? $25 and I'll throw HF toolbox that I carry it in. ;-)