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I have tried three Celestron Xcel's - 8, 12 and 25mm though I only had the chance to try them critically against some bright stars on a Celestron 9.25" f/10 SCT. In short: very similar to the old Vixen LV's, in that they:
- have good eye relief around 20mm;
- are bright and contrasty,
- lack noticeable flare or internal reflections on bright objects,
- display some pincushion distortion
- a slightly larger field of view (60 degrees) than budget eyepieces (typically 45-50 degrees);
- no noticeable coloration on Jupiter or the moon.
The only downside I found is that two of the eyepieces I tried had a hint of lateral colour when a bright star was pushed to one edge of the eyepiece, but were sharp on the opposite side; and rotating the eyepiece confirmed the aberration was in the eyepiece, not the scope. This suggests a smidgen of wedge error or decentering in one of the lenses, HOWEVER the amount was small and most observers would never notice it.
I didn't have a chance to try with a fast Newtonian or refractor so can't comment on whether they are a good match for that type of scope.
They ARE a good midrange eyepiece and compared well against my set of Vixen LVW's. Also you'd have to wonder why the ES 68 degree series are so huge for just another 8 degrees in the apparent FoV.
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