The ban won't necessarily hurt HTC although presumably some level of financial recompense will be attached to the infringement something that HTC's dwindling coffers can ill-afford to service.
More worrying is how many of HTC's current devices are also likely to be infringing upon the patents and would therefore be at risk of being banned themselves.
HTC will no doubt be studying the impact of the ruling closely to minimise the effects to its business.
Nonetheless its probably fair to say that this judgment couldn't have come at a worse the for the Taiwanese company, already beset with sales and revenue worries that could sink the business as they stand.
Maybe a HTC phone is worth buying today, because soon - like Palm and Nokia (possibly Blackberry) - that opportunity may not exist anymore.