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Michael, 
I just recently went through this ordeal myself, comparing our traditional older mercury lamp and housing to:
1. 120w EXFO
2. Lamba Ls from Sutter (xenon)
3. Zeiss' new mercury housing system

I was quite impressed by, and excited, to try Excite's system, as so many people have given it a thumbs up. Anyone reading the material on the system, it sounds fantastic. 
However, although it was VERY user friendly, the brightness I was observing was not satisfactory. We tried several things to improve this, but the reality was that for our Axioplan, it just did not seem to do the trick. Using the same exposure times as our traditional mercury system resulted in dimmer images. Not setting exposure times resulted in slightly brighter, but much longer exposure times. 
Same for Sutter Instruments, which for us was the better of the 2. 
Surprisingly, the new housing and collector lens on the Zeiss (I believe this unit was just realeased in the past year) resulted in the brightest signal, shortest exposure, at all magnifications. So the traditional mercury with a new housing and collector lens (much bigger housing) worked best for us.

All the bulbs are easier to exchange and the illumination fields very comparable on the new systems compared to the older mercury housings. The most important thing I found, was in addition to the housing system, the collector lens/adapter to your individual scope makes a HUGE difference. 
Also, obviously, the common wavelengths that you would be trying to detect may also influence which system you go with. Mercury lamps have peaks, Sutter's is pretty high, and flat, if I remember correctly. You can get the specifics from the websites and reps.  

Realistically, they all have their pluses, and if you have multiple systems that need replacing, and the budget, it would be fun to have all 3.  But the image qualities on our particular system made enough of a difference for us to choose Zeiss. I've been using it for almost a year and I am still pleased with the choice. 

I would highly recommend getting in touch with your local reps, ours were extremely helpful, and it was difficult to turn down each system and choose only one. Try the systems directly on the units you plan on using them on, as seeing for yourself and testing them really pulls out those details that are different for everyone. 

I hope this helps, good luck!

Melissa

Melissa A. Gonzalez
R&D Cell Genesys, Inc.
South San Francisco, CA 94080
(650) 266-3168


-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On Behalf Of Michael Weber
Sent: Thursday, April 13, 2006 7:45 AM
To: [log in to unmask]
Subject: experiences with exfo x-cite illumination system?

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Dear list,

you probably know the EXFO X-Cite 120 illumination system:

http://www.exfo-lifesciences.com/products/X-Cite120.html

It's an "alternative" to common lamphouses with HBO-/XBO-lamps, with a 
halide gas lamp in an external box, plugged into the microscope beampath 
  over an optical fiber.

On the paper, this system sound interesting, especially when it comes to 
heavy-used machines. The running time of a lamp is to amount to 1500 
hours. Beyond that, there's no need for adjustment like on normal 
(non-motorized) lamphouses.

We currently have one of these illumination system here for demo from 
Olympus, but only togehter with a less used microscope. Therefore, we 
still have no long-term experiences with that system:

- Is the running time realistic?
- When needs the fiber to be changed in reality?
- Is the output and the spectra stable over the whole lifetime?
- How is the spectra compared to other lamps?

So far I found one review, but this sounds more like advertisement:

http://www.biocompare.com/review/246/The-EXFO-Photonics-X-CITE-120-Fluorescence-Microscope-Illumination-System.html

We have quite a lot of lamphouses here on our systems, and most of them 
are heavily used, so we need to exchange the lamps quite often. Exchange 
and adjustment costs always some time - so maybe it's worth switching to 
another illumination system?!

I'm really interested in your experiences with the EXFO system.

Have a nice Easter,
Michael

-- 
Michael Weber (B.Sc.)

..MPI..
Max Planck Institute of Molecular Cell Biology and Genetics
Light Microscopy Facility
Pfotenhauer Str. 108
D-01307 Dresden
phone: +49 351 2102837

..MTZ..
Technische Universität
Medical Theoretical Centre, Haus 91
Fiedlerstr. 42
D-01307 Dresden
phone: +49 351 4586426