I get the 'H' all the time
Wrong on no 'H' icon. You're not getting HSDPA. This is a problem with providers. I had to fight with T-Mobile techs to get them to 'activate' my 'enabled' HSDPA. This was after fighting with the Customer Service agents who swore I had to pay another £10 pm to get it.
If you're on T-Mo, you show 3G until an actual data transfer starts with GPRS. Then if the signal has 3 bars, it will switch to H.
I get the 'H' on P750 with T-Mo at my desk on the 9th floor at Canary Wharf, and speeds from 900K to 1.3M bps.