Switched from Orange last week, after they told that that despite being a pay monthly customer with them for over 5 years, the plan i was on on "did not acrue any loyalty".
I promply showed then what loyalty was....
I picked up a HTC Hero from T-Mobile for £62 for the phone, on a £10 a month plan that includes unlimited internet (3GB fair usage), and one bolt-on of your choice (unlimited landline calls, unlimited texts, unlimited calls to other T-Mob) and comes with 100texts and 100minutes a month.
You can of course get a HTC Desire on the same £10 plan for £160 for the phone, and still enjoy unlimited internet and the unlimited texts or calls.
Basically Orange charge £25 a month for this, and have a dumb 500MB data limit.
My only fear of course, is that when Orange and T-Mobile merge, they don't become a decent T-Mobile, but a crappy Orange...