You won't be disappointed. I also wear bifocals and have used PDM since getting into scuba. In fact, I'm having my bi-annual eye exam this weekend and will be sending off yet another mask to PDM along with my prescription next week.
The only downside to a prescription mask is that it makes the mask a very expensive piece of gear. So I use Pelican boxes to protect my prescription masks whenever I go diving. Those flimsy plastic boxes that come with the masks just won't do.
And although it's expensive, a prescription mask is worth every penny!