The OAG is very solidly constructed, but there is one major flaw and that is the helical focuser, which is very flimsy compared to the rest of it and the lets the overall quality down. I ended up screwing it right down, locking it and using a Baader T-thread to 1.25" focuser, which is solid as a rock.

After much deliberation I ordered and received the OAG to be able to use on my 9.25" SCT at home where dual-mount or piggy back scopes are out of the question.
Out of the box the build quality is excellent, nice sleek and black, with perfect looking threads and a really sturdy and solid feel, should fill all with confidence. The thickness means that I have no concerns about it causing any sort of flexure on my setup.
So, firstly to fit it to the EFW2, remove three small grub screws present on the outer casing on the wheel, line up the holes on the OAG with the wheel and fit the supplied bolts, tighten with allen key and voila! fitted!
That was simple wasn't it?
Now, fit the 2" nosepiece to the front of the OAG (the one received with the EFW), the 2" to SCT adapter and screw to the scope (6" SCT)
Fitting of the Atik 314L to the back is simple, remove the supplied nosepiece from the 314 and it screws straight on to the back of the EFW2 as before.
Atop the OAG is the fitting for the guide cam, I'm my case an Atik Titan. There are several spacer rings supplied with the OAG to enable you to achieve focus with the camera, each of varying thicknesses. The focus lock screw feels secure and on undoing the helicoil focus ring is able to turn and gives you a very smooth focusing adjustment of several millimetres. So, on with the camera atop all three spacer rings, again remove the 1.25 nosepiece from the Titan and it screws directly onto the top of the OAG, anyone would think these were made to fit with each other, funny that :o).
So, outside and on to a star, lined up with 314 and focused with Bahtinov mask, no problems so far. Then on to guide cam and after a small amount of slewing a nice sized star comes on screen, or should i say a giant doughnut, time to focus.
Focusing from one limit to the other on the focusing ring just alters the doughnut size, certainly no focusing spikes from the Baht. mask. Then the inevitable cloud rolls in, no more set up possible.

Round 2
Now down to my dark site a few nights later and beautiful clear skies, hooray. On with the kit and same procedure as before, star now focused on imaging camera, No amount of adjustment could get focus on guide cam so removed it and removed one of the spacer, closer focus but still not enough.
so lets remove another spacer, oh dear, these two spacers are so tight against each other I could not separate them without possibly irrevocably damaging them. Decided to try with no spacers and focus was almost perfect but not quite, the camera had to go down slightly further than the focuser would take it. Then sudden brainwave, the prism inside was extended out as far into the light cone area as possible, perhaps I could move it up a bit and get it within the focusing region, Great idea.. oh no problem arose..
To move the prism there is a small grub screw on the outside, just slacken DO NOT REMOVE (big warning on instructions) but then to move the prism you have to move it with your finger ??? mmm.. not sure about this design feature.
To get to the prism I had to disconnect all camera cable etc.. and remove the whole assembly from the back of the scope (messing up my goto no doubt with the undoing and refitting), slacken the screw and push the prism up a little back into the body of the OAG and retighten the screw. now put the whole lot back onto the scope and try again.
Now, align with star on imaging cam and focus, looks good, onto the guide cam and a small doughnut appears, adjust focusing ring, lovely spikes from Baht. mask, lock focuser.. nice firm lock and no signs of any play in it. Back to imaging camera and that too is focused, so they are now par focal and I am ready to rock and roll, fired up phd and did several target and only on one did i have to move the object just off-centre of the image to find a guide star, so very pleased. Still not done a long session with this set up but the only thing that could spoil it now is the weather or me.

In summary (after that long ramble)

Pros
Build quality - excellent
Fit to other Atik products - Excellent
Focuser for guide cam - excellent and smooth
Ability to find guide stars (from quick session) - Very good

Cons
No way to adjust prism angle, just height (not sure if this is ever necessary so maybe ignore this)
No external adjuster to change height of prism from camera, having to split the rig apart just to move the mirror with your finger seems a little strange, an adjuster on the exterior would have been very helpful indeed.

I hope you find this review helpful.

Dave