I have had my Omega for 7 years and it has been extremely reliable apart from a few faults. 1) Alternator over voltage stopped the auto transmission from changing gear:- replaced alternator. Cam sensor replaced due to difficulty starting and unable to idle. Present fault with uneven idling, can even stall. Looks to be a common fault with the idle valve. Clean it or replace it.
These cars are so cheap to buy after 1 year's depreciation. A lot of car for your money.
I have a 1996 Omega 2.0 automatic and have just started having the engine stalling when idling. Diagnosis is that the crank shaft sensor is broken and hence needs replacing at a cost of around £200. Hopefully that will solve the problem. A friend of mine had a 1996 2.0 16V Vectra that had problems of this nature and has still not been resolved. He's had two new cam shaft sensors and two new crank shaft sensors still with no joy. I don't know if they have the same engine, but the likelihood is high!
I wrote the comment dated 13th July 2002 about having my transmission fluid changed on my 2.5 CDX V6.
As a follow up, I did have the fluid changed by a Vauxhall dealer shortly after I wrote that comment (cost about £70 I think). I didn't notice any difference (was fine before hand anyway). I sold the car to my sister two years ago. She is still driving it with no problems. I don't regret having the fluid changed as it may now be preventing problems from occurring (you wouldn't notice any difference when you change your engine oil either!).
I owned the car for two years and spent about £900 in maintenance over that period. I was very happy with the car and very much regret selling it. The only time it let me down was a flat battery due to faulty alternator. Replaced alternator and no further problems.