for me it was a combination of a lot of things........
1) Brand - Many years ago i worked for Vauxhall, about the time that the Omega came out, i always struggled to understand why Vaux ditched the Carlton/Senator and then expected 1 car to replace it, i have never really been into foriegn cars and i have an aversion to anything with an oval badge on it. In the past i have had a lot of cavs, especially Mk2's i love them, they were my 'weapon of choice' in my boy racer days!!
2) price - i was looking for something that would cover a lot of miles, would be reliable, could do the 'european run' when required with the kids not moaning that it was like a sardine can, we had a Zafira prior to this and that used to rev its head off at 70mph, the replacement would have to have been comfortable as well.
I had a strict budget of £3500 when i was looking for mine, it had to have less than 100K on the clock and had to be a light colour, i was down to a handful of cars:
7 series BMW
Omega Elite
C or E class Merc
The 7 series had the wrong image for me (sorry to all those BM drivers) the Merc didn't have enough toys and the Omega i found i didn't like originally, i wanted a prefacelift, never really like the look of the facelift models.
However it fitted the bill perfectly, since then i have done 40,000 since april '06, it has been utterly reliable and have served me well, however i have a feeling that it will be time to part company soon and so she will be up for sale.
Her replacement......another 2.5 Elite, but this time i will get the LPG conversion done so as to save money.
There are so many other reasons why i bought her, but i suppose value for money was the one that stood out the most.