I got the FFCX exactly because it could do dual extrusion. Have a separate build material and support material. Though everything would be easy peasy. When I got the printer I struggled getting it to work; the prints were awful (messy and imprecise). I also couldn't get the solvent for the support material (D-limonene for HIPS).

So I gave up on the idea. Removed the second extruder to save weight and did mono-material prints for about a year. This works better then you might expect but requires a lot of post print finishing.

In the last few months things have changed. Firstly I know my printer's mood like the back of my hand. It has been mechanically fine-tunes to perfection (a work in progress, mind you). Like-wise with the software. Makerware can take you very far, provided you take the time to learn how it works. I also found a D-limonene supplier. So the experiments began.

Right of the bat I got good results. Experience really does make a huge difference. I have some photos of my last prints for clients; really intricate stuff. I hope to post these later today or maybe during the week. I am quite busy with real-life work and stuff. The results I get now are on par with any print I have seen from big-name printers like Stratasys and the like and at a fraction of the cost. These days printing with support is out of the question unless its something simple for around the house.

To answer your questions:

1) Using dissolvable support opens doors, believe me. But you must get to know your printer inside and out. This goes for all printers. Be prepared to tinker and upgrade overtime.

2) FFCP vs Ultimaker: two very different beasts with different pros and cons. FF's have direct drive extrusion; the Ultimaker has Bowden. Direct drive is a better choice for dual-extrusion as you have more control over your extrusion volume and output. On the other hand direct drive adds weight to your carriage which can result in corner ringing. You can counter this by slowing your print down and playing with the acceleration settings. Ultimately you won't get the print speed of an Ultimaker though. Personally I print outlines at 25mm/s to 50mm/s and get a fantastic finish; for others that is too slow. Both printers need to be fully enclosed to print with ABS so no difference there. As far as layer height goes the Ultimaker can go down to 0.02mm, the FF to 0.1mm. From a purely technical aspect the FF's steppers can go that low too. In fact they are better suited to go that low than the Ultimaker steppers but the direct drive of the extruders limits the minimum flow rate. Adding a gear to step down the extruder revolutions and you can very easily as fine a layer as the Ultimaker. Again, its all down to your technical aptitude and desire to tinker. FWIW I successfully printed at 0.05mm layer height on my FFCX with out any mechanical modification, just by adjusting the flow output. However that layer height coupled with the slow print speed results in the print taking a very long time.

The Ultimaker has drawbacks. Firstly it is very expensive compared to other printers. You could get two FFCP's for the price of one Ultimaker. It also uses an odd sized filament i.e. 2.85mm. Common sizes are 1.75mm and 3mm. I've heard that some people are suing 3mm filament on their Ulttmakers but cannot confirm.

Things I don't like about my FFCX: Its quite noisy. Not industrial machine noisy but if its running at night then I have to close the doors. I don't like the colour either (black). I will probably strip it at some point and spray it either white or silver (like the UM .

There are other brands worth checking out. High on my list are the TAZ5 and the Robobeast. Both will need enclosures made of to be used with ABS.

Hope that helps.