I purchased a Tormek T7 last year (from Dictum) and could not be happier. I asked a similar question on here before buying and most people told me to avoid it.
I knew a few people that used it daily and they convinced me to give it a try or sell it on. As it happens I got a fantastic deal from Dictum which was cheaper at the time and with the low euro as well I save about £150 off UK prices. I figured I could try it for a month or two and sell on at the same cost to me if it didn't work out.
First off, yes it is slow when removing large amounts of metal however that's kind of the point of the tool to some degree - it removes metal but retains the temper. However we are talking minutes here, not hours and it's really not an issue in the grand scheme of things. After the initial grind, maintaining and honing your edge is simple and quick. It's messy but I make provision for this in where I store and use it. This is definitely a keeper.
Be aware that whilst there are plenty of similar machines as mentioned in your list, not all of there respective stones last as long and this could increase the cost of ownership comparative to a Tormek depending on use.
For reference btw, another similar machine is the Jet (
http://www.axminster.co.uk/jet-jssg-10- ... ner-200336).
As others have said, it's not really the tool to flatten backs although you can get horizontal machines that will fulfill this aspect. I use a set of Ohishi stones for flattening but then this is usually a one time process per tool for me.
The Sorby Pro Edge certainly has it's fan base and I've yet to know anyone who bought one who regretted the purchase so definitely worth looking at as well. That said, I don't see myself what advantage it has over a good narrow edge sander other than a decent tool guide and these can be bought third party anyhow.
In reality it all depends on what you want to achieve and with what tools.
