a lot of ex poly's are making a name for themselves by forming good relations with industry as opposed to older institutions such as the red bricks, who often pay less attention to that element and focus on the more traditional stuff like research.
It all really depends what you want out of a uni. I started off at an ex poly (stafford) who have some excellent ties with Microsoft, HP, Eurocopter, Syngenta etc etc I got a placement at HP through them but could just as easily have been MS or even Eurocopter in Germany. Many of my friends went on to places like Cisco, MS, HP simply because of the universities ties.
As it stood my 13 months at HP made me absolutely despise the corporate world, so I shunned it for many post grad degrees at a more traditional uni (who let me in on the merit of my "poly" BSc no questions asked) and it now looks like i'll probably end up leading the academic life, at least for a little while.
Either way though, I personally dont think the ex Poly's carry too much stigma anymore, and for those only interested in a industry career after their degree, they could even be the better choice in some instances with more focus on the student and their follow up career rather than pure research.
Saying that, Manchester students tend to end up working for huge banks rather than HP and MS and other industry giants, and i can tell you right now, if its money you want then banking is most definately where its at, not being a programmer at MS or HP...